Hybrids and the economics of specialization

 Massively multiplayer online games (MMOs) typically have multiple classes of characters, some of which are specialized for a single role, and some of which are hybrids which can serve in multiple roles. These hybrid characters are a common failure point for MMO design, often ending up much weaker or much more powerful than more specialized characters. 

Fortunately, there are some basic economic models of behavior that can be used to understand the design pressures that can distort the role of hybrids in MMOs. By having a clear concept of why these pressures occur and what conditions enable these pressures, we can systematically create conditions which promote both hybrid and specialist classes simultaneously, creating complex and fun gameplay for our players.

What's a hybrid?

In classic role playing game (RPG) design, there are commonly three primary character archetypes: tank, DPS ("Damage Per Second"), and healer. These archetypes have their roots in old-school pen and paper RPGs like Dungeons & Dragons, and were carried forward into early single player RPGs like Ultima and then into MMOs.

The three primary archetypes are:

In the standard model of RPG combat, the tank holds the dragon's attention and takes the brunt of the dragon's damage, while the healer keeps the tank alive and the DPS kills the dragon. Each player is performing a single role using a character specialized for that role. For example, tanks generally do little damage themselves, but maximize their ability to withstand damage for others.

In the nomenclature of MMOs, a "hybrid" is a character that bridges two or even three of these areas. In MMOs set in fantasy worlds, a tank is commonly embodied as an armored medieval knight while a healer takes the form of a priest or cleric. If we create a hybrid between a tank (knight) and a healer (priest), we get a paladin who can wear heavy armor and cast healing spells.

Why are hybrids difficult to design?

At the heart of the hybrid problem is the fact that if a hybrid can perform a given role as well as a specialist while also having other abilities the specialist can never have, playing a specialist becomes pointless.

To put it in terms of our earlier example, if a paladin can tank as well as a knight but can also heal, then there is never a reason to play a knight instead of a paladin. If the hybrid has all of the advantages of its parents plus extras, then the parent class is doomed to extinction.

Conversely, if a hybrid is always inferior to a specialist in any given role, then it's always better to have a specialist fill that role. As game designers, we want to create a vibrant ecology of classes, where players have a wide variety of classes and playstyles available to them.

The standard solution to this problem can be summed up in the phrase "Jack of all trades, master of none". Hybrids are generally made less effective in each area than their parent classes, with the intent that they make up the deficiency with their abilities from other areas. The paladin mentioned above might not be able to survive as much damage as a knight, but they can heal other players and help them survive, something a knight could never do.

Historically, MMOs have had a great deal of difficulty designing hybrids that are powerful and valuable without completely displacing their parent classes. The catchphrase for these overly successful hybrids is "tank-mage". This term comes from the early days of one of the first MMOs, Ultima Online, where some characters could both wear heavy armor and cast powerful damaging spells. A tank-mage could both take and deal a lot of damage, creating a character that was superior to any other type of character in most situations.

Since Ultima Online, other MMOs have tried to avoid this problem, but players inevitably gravitate towards the latest incarnation of the tank-mage whenever possible. This is not a sign that the players are cheating or deliberately trying to abuse the system, it's just the natural result of players trying to find the golden path and "win" the game. A character who can take more damage is better and a character who can dish out more damage is better -- therefore a character that can do both is ideal.

For example, in City of Heroes the Fire/Fire Tanker emerged as an early tank-mage contender because of its high damage resistance and ability to deal lots of damage to multiple enemies at one time.

The discovery/creation of these tank-mages by players is the product of the incredible ingenuity of MMO players and the complex emergent properties of the game systems, rather than any particular failure on the part of the design teams, and they are mostly adjusted or "nerfed" as they become apparent. However, nerfs generate turbulence in the player community, and it is always better to prevent these sorts of issues from arising in the first place.

The hybrid issue is exacerbated by the fact that MMOs are both solo and group games. If people only played MMOs in groups, a character able to soak a lot of damage but deal no damage would be viable because the other people in the group could deal damage for them. The individual character could be one dimensional (a pure tank) because the other group members fill out the other two parts of the trinity (DPS and healing).

However, studies have shown that even in group-focused games, players spend a lot of their playing time doing things on their own. Even if a character is the best healer in the world, if they can't take or dish out at least some damage they won't be able to operate outside of a group. Soloing requires that the character be able to deal damage, plus the ability to absorb, avoid, or heal the damage taken.

Therefore, once the design decision has been made that every character should be able to solo -- a decision that has been made practically mandatory by the successful example of World of Warcraft -- it automatically follows that every character must be a hybrid and therefore subject to the paradoxes of hybrid design. This is a universal problem, not just one that affects certain classes within a game.

The party economy

 Ok, enough background. If we think about our character classes as characters, our mental models are going to be shaped and limited by other games and other forms of fiction such as books and movies. Authors don't have to worry about Robin Hood being overpowered because he has high levels of both ranged and melee DPS, but game designers do.

Instead, I'd like to propose a much less warm and fuzzy way of analyzing the give-and-take between classes. The natural psychological forces pushing players towards tank-mages and character specialization are relentless, and the barriers we put up to stop them must be equally unromantic and purposeful.

What I'd like to propose is a simple framework for connecting MMO design to economic theories of human behavior, with the intent of providing some useful tools for thinking about class design. I am most assuredly not saying that everything about games can be described in economic terms, or that economic theory can be blindly applied to game design.

What I am saying is that there are some clear analogies to be made between class/party dynamics and some basic economic theories, and that a thoughtful exploration of these analogies produces a useful framework for thinking about class design plus a number of practical recommendations.

The fundamental bridge between these two areas is the idea that any group of characters, from a duo to a hundred-player raid, can be thought of as an economy with the characters serving as both producers and consumers.

There are a variety of "goods" or "products" that the characters create and consume, such as healing, damage, tanking, buffing/debuffing, crowd control, and utility abilities like stealth and summoning. These goods have costs, either explicitly (casting a spell requiring mana) or implicitly (opportunity costs, where every moment you spend casting a healing spell means you're not casting a damaging spell).

Every time a character benefits from what another character does, they're participating in trade with that character. When a tank holds the dragon's attention so that it doesn't attack a teammate, the tank is trading their production of tanky-ness to the other character.

Presumably the other character is producing and trading something the tank needs, such as sufficient healing to keep the tank alive or enough DPS to kill the dragon. Together, the group produces enough of each key commodity (tanking, dps, and healing) to complete their goals as a group.

Absolute and Comparative Advantage

The principle of absolute advantage was developed by Adam Smith in the late 18^th century to describe some the effects of international trade. Smith wrote:

"If a foreign country can supply us with a commodity cheaper than we ourselves can make it, better buy it of them with some part of the produce of our own industry, employed in a way in which we have some advantage." (Wealth of Nations, Book 4, Chapter 2)

This is a clear argument for specialization, and the analogy to MMO classes is obvious. In a situation where each character has a role where they're the best (an absolute advantage), they should specialize in that role. However, hybrids can never be the best at any role, or they would replace their parent specialist class completely.

In that situation, we turn to a closely related theory called "Comparative Advantage". Attributed to David Ricardo and Richard Torrens, this theory states that each entity (countries in their examples, classes/characters in ours) has an area of production they're "least worst" at -- their area of "comparative advantage" in comparison to the other entities in the economy.

In our party economy model, consider the following ten character party makeup:

In this example, the hybrid character has a comparative advantage as a healer. The specialist DPS characters can produce DPS more efficiently than the hybrid can, and the specialist healing character can heal more efficiently than the hybrid can.

However, since there are lots of DPS characters present, the hybrid is going to be pushed towards healing, an area in which he has a comparative advantage over most of the party. He doesn't have an absolute advantage (the healing specialist does), but the presence of so many other DPS characters in the party economy means that his greatest contribution will be as a second healer rather than as an eighth DPS character. He has a comparative advantage as a healer and a comparative disadvantage as DPS.

The interesting thing here is that the hybrid has a comparative advantage as a healer even if the hybrid is a more efficient/effective producer of DPS than the specialist DPS characters. The strengths of a character in isolation (their soloing abilities) are irrelevant; it's their relative value in a particular group composition that drives the character towards one role or another.

Furthermore, if that hybrid character is always pushed towards healing, their player will begin to wonder whether they should have just chosen a dedicated healing class in the first place.

Class design as market inefficiency

In a perfect world, universal specialization leads to maximum productivity for the economy. From a game design perspective, there are two things wrong with that statement.

First, we don't want everyone to specialize. We want both specialists and viable hybrids that can serve in two or more roles. There are relatively few primary roles, and unless we have viable hybrids, the game is going to end up being extremely simplistic.

Secondly, we don't want maximum productivity. We want whatever level of productivity matches the intended challenge level of the game with the most fun group dynamics. From a certain point of view, a game designer's entire job consists of putting barriers in the players' path. They're supposed to be interesting barriers, obstacles that provide flavor and enjoyment, but they're still barriers.

The key phrase here is "in a perfect world". The economic laws mentioned above are predicated on certain assumptions, and as long as those assumptions hold true hybrids will experience strong implicit pressures to specialize.

Therefore, the essence of hybrid class design becomes violating these assumptions to create an imperfect world. A perfect party economy is a boring party economy, with everyone forced into fixed roles and no nooks and crannies for hybrids and unique classes and playstyles.

Not all of the assumptions have to be broken in order to create a viable niche for hybrids, but multiplayer gameplay is messy and we can't rely on any one trade barrier to stem the pressure that naturally destroys hybrids. Players find ways around the limitations we build into the game mechanics, so the more redundant barriers we include the more likely we are to have the effect we want.

Breaking assumption #1: Homogeneous output

One of the fundamental assumptions of the comparative advantage model is that a commodity is the same no matter who produces it, that a bushel of wheat from one country is equivalent to that produced by any other. In MMO terms, this would mean that all healing or tanking is the same, even when produced by different classes.

If all tanking is the same, then all tanking classes can be directly compared to one another and one will inevitably come out on top. This would lead to a pressure on characters in the optimal tank class to specialize in tanking and all other tank-capable characters to specialize in other areas.

We can break this assumption by offering different "flavors" of the three basic commodities. If one type of tank is better at absorbing magic damage, while another is better at absorbing non-magical damage, then we have split the single commodity into two commodities, which can be supplied by two classes. The more commodities, the more potential for hybrids who can fill multiple niches.

Just creating the flavors in the basic game mechanics is the first step, but it must be supported throughout the game by ensuring there is a demand for all flavors. Making one type of tank better at absorbing hostile magic is pointless if there is not sufficient hostile magic out there to be worth tanking. To put it back into economic terms, non-homogenous output must be matched by non-homogenous demand.

Breaking assumption #2: Free entry and exit from the market

Another assumption is free entry and exit from the market, the idea that producers are entering the market when it's to their advantage and leaving it when they no longer benefit or can't compete. In an MMO, this idea manifests as swapping characters in and out of a group for different tasks.

If the group is going to do a fight that requires extra healers followed by a fight that requires extra tanks, they can achieve maximal efficiency by adding extra healers to the group for the first fight and then swapping them out for additional tanks for the second fight.

This is a perfect example of a potential hybrid (a healer/tank) being displaced by two specialists. Because the specialists can enter the market freely when it's convenient and leave when it's unprofitable, they can out-compete a hybrid who must divide their strengths between two roles and stay in the market full time.

The City of Heroes Task Force system is a great example of a game where the design does not allow free entry and exit from a group. A Task Force is a series of linked missions, and the group of players present at the start of the task force is locked in to the task force. Players can leave the task force, but new players can't join.

This sort of lock-in produces a counter-pressure to the natural specialization pressure, encouraging players to take a more balanced approach. As with any design decision, this counter-pressure comes with a cost. Players like being able to log off when they want to, and may be less likely to join a Task Force if they know they are locked in until the end. Also, the hordes of newer, casual MMO gamers who have started playing in recent years are unlikely to appreciate a game which is unforgiving of real life interruptions.

An alternative model is the World of Warcraft raid ID system, where players can only participate in a given raid once per week. If a raid group swaps in an extra DPS player for a single fight, that player is then barred doing that raid again for the rest of the week. This potentially could make the player or group think twice about using up the entire potential week's contribution of that player for a onetime benefit.

Breaking assumption #3: Steady State Consumption and Production

The model as I've described it so far is a steady state model, where each producer has fixed efficiencies and fixed requirements.

However, if the supply and/or demand change due to circumstances, this can mean that the comparative advantage of a hybrid character could change over time as well.

This assumption needs to be broken in conjunction with the assumption of free entry and exit to the market. If players can enter and exit freely between predictable changes in circumstances, they can always adapt the group as a whole to the new circumstances by swapping in different specialists. However, if there are no changes in the demands made on the party, then there is no need ever to change the party balance.

One common method to change up requirements is to have fights that consist of multiple phases or waves. For example, consider a boss fight where players are attacked by multiple waves of enemies.

One wave could consist of a single enemy that did lots of damage, requiring a single tank and multiple healers to keep the tank alive, while the second wave consists of multiple enemies to be tanked separately, and the third could do damage that cannot be healed until after the enemies are dead. By varying up the requirements between waves, we create a niche for characters which can change their production.

The primary challenge in breaking this assumption is to break it pervasively throughout the game design. It's not enough to add a single fight that requires extreme numbers of tanks (such as the Four Horsemen fight from Naxxaramus in World of Warcraft), because that puts enough strain on groups of players to hurt without creating an ongoing need for more tanks. It becomes simpler for the players to solve the immediate problem ("Find an extra tank for tonight") than to make a permanent adaptation ("We need to make a hybrid tank/DPS character part of our regular team").

Breaking assumption #4: Continuous production

Hitting a perfectly specialized balance of producers and consumers requires there to be smoothly adjustable levels of each. Production within a party is a step function, because the party always consists of a whole number of characters. As the size of the party increases, the relative size of the change of adding one more character becomes smaller.

If you have one healer in the group, adding a second healer increases the total healing production by 100%. If you have 100 healers in the group, adding one more healer increases the group's healing by only 1%. The larger a group of players, the closer the group can approach an ideal distribution of production using only full specialists.

Because hybrids are by definition weaker in any given role, adding a hybrid to a group provides a fractional increase in each of their areas of production. The smaller the group of players, the more useful those smaller increases are in hitting an optimal balance within a given number of players. If you have a three-person party and you need an equal number of tanks and healers, then adding a healer/tank hybrid character who is 80% of a tank and 80% of a healer makes sense.

Most MMOs have a maximum size for a party of characters in the single digits. (Five for World of Warcraft, six for EverQuest, eight for City of Heroes/Villains, etc.) This is small enough usually to make the addition of a single player a significant change in the party balance.

However, most MMOs also have larger "raid" missions where groups of twenty, forty, or even more players all cooperate to achieve a major goal. In these larger fights, it's possible to create the required party balance using only specialists, squeezing hybrids out of the mix. In general, smaller groups create a more stepped production function which creates more niches for hybrids.

Breaking assumption #5: Free trade

Another assumption in this model is that all parties can trade freely with all parties, without any tariffs or other trade barriers. The ideal solution for maximum productivity assumes that everyone specializes where they have a naturally occurring comparative advantage, but adding in things like tariffs to make foreign imports more expensive can shift the balance points. These trade barriers represent a sacrifice of pure efficiency in order to achieve other goals, such as maintaining a certain minimum of domestic food production.

In a game context, this means that not every commodity produced by a character can be cleanly transferred to any other character. For example, a given type of healer might be better at healing some classes than others, creating a need for multiple types of healers in order to cover all their teammates.

A sample fight mechanic that would represent a trade barrier would be a battle that requires the players to split into two groups that stand too far apart for mutual support. It doesn't matter how efficient it is to have a single highly specialized healer if their output can only reach half the party. At this point, a hybrid DPS/healer who can step up to cover the second group for a short time becomes an asset.

Another example of this principle is those fights that involve all players present getting hit with some damage. In this case, every player has to produce their own "tankness" in order to survive the initial hit, even if other players can heal them afterwards.

Instead of maximizing just their own healing or DPS ability, they have to split their production to provide some level of damage avoidance/absorption as well. This keeps players from over-specializing into pure "glass cannons", who can do massive damage but die when an enemy breathes on them. One existing example of a fight which breaks this assumption is the Leotheras the Blind fight from WoW, where every player must be able to defeat a weak enemy without help from their teammates.

Special case: Natural monopolies

One place where a balanced network of trade between classes breaks down is in the tanking monopoly. In the classic dragon example used at the very beginning of this article, the dragon is hitting only one person at a time.

You can have dozens of DPS characters all adding their output to create a single volume of DPS, but tanking is generally not additive on any single enemy. If the dragon can kill the tank with one swipe of a claw, having two tanks doesn't help. The dragon swipes once, kills the first tank, swipes again, and kills the second tank, then goes on to eat the rest of the group.

This creates a natural tanking monopoly and punishes hybrid characters who try to enter the tanking market. In any fight where there is a single enemy to be tanked, all hybrid tanks will be pushed towards their alternate roles as healers or DPS because the monopoly prevents them from competing as tanks. Since this "one enemy, one tank" condition is the default for most MMO fights, it works to devalue hybrid tanking characters across the board.

One solution to this monopoly is to add mechanics which require multiple tanks for key enemies. For example, fights where the primary tank is sometimes teleported away from the fight for 10 seconds would reward teams for taking a hybrid character who could tank for at least a very short period.

In a situation where there is a limited team size, it wouldn't make sense to keep a second tank waiting around the entire fight for such a short window of usefulness, but a hybrid that could both tank and DPS would be desirable. This could also be considered an example of breaking the "steady state" assumption described above.

Special case: Economies of scale

Another issue that can produce market distortions is economies of scale. In a lot of domains, the cost per unit of production is cheaper for large producers than for small producers. This can mean that anything that increases production (say, a piece of equipment that is used for healing, or even an inherent character ability like a healing spell) does more good for a class that already excels in that ability (in this example, healing).

In games this principle often manifests in the synergies that occur when a character is highly specialized. For example, if a DPS character has access to two abilities that each increase their damage by 50%, the net result is a 125% increase in damage because the second multiplier acts upon the first as well. Therefore, a lone character with both these abilities will do more damage than two characters each with a single ability. Even if both a DPS specialist character and a hybrid character have access to identical abilities, they are generally more powerful in the hands of the specialist.

Typically, hybrid characters have their abilities split between multiple areas, and those areas do not reinforce each other. This lack of synergistic effects can make hybrids even less competitive with their specialist parent classes than they might appear at first glance. If it's always easier for a specialist to increase their output, then hybrids will inevitably get progressively squeezed out of the market as characters become more powerful.

Special case: Unique Abilities

One route to making hybrids desirable has been to provide hybrid classes with abilities that do not exist in any of the specialist classes, such as the ability to resurrect their allies in combat or provide powerful unique buffs. However, if all members of the hybrid class have the special ability, it doesn't affect the natural pressure to specialize.

If paladins already have a comparative advantage as healers, that's still true even if their unique buffs are desirable. It may provide a good reason to bring a hybrid instead of a specialist, but the hybrid will essentially be playing a specialist role.

Alternately, if only some members of a hybrid class have the special ability, then it simply shifts the optimal point of specialization. If these unique abilities are too strong, they can be considered as commodities in themselves and thus subject to the exact same specialization pressures as described above.

This is not to say unique class abilities are a bad idea; they've historically proven to be a very useful tool for encouraging players to create teams with a good variety of classes. But they do not remove the basic pressures that push all hybrids to focus on producing the single commodity in which they have a comparative advantage. Thos pressures must be fought by breaking more fundamental assumptions.

Beyond the trinity 

The idea of the three primary archetypes (Healer, Tank, and DPS) is pervasive enough in the genre as to be referred to as the "holy trinity". However, it's not the only way to break down the possible commodities in an RPG. Some designers use six categories, others use only two (increasing damage out and decreasing damage in).

Some of the alternate categories are things like "buffers/debuffers" specialized in enhancing their allies or debilitating their opponents, and "crowd control" specialized in rendering opponents helpless by rooting them to the ground, freezing them in blocks of ice, etc.

The exact number of commodities isn't important in this analysis, as long as the commodities are not perfectly interchangeable. For example, if the DPS can kill a group of enemies before the enemies reach them, there's no real need for tanks or healers. If freezing an enemy in a block of ice can completely remove the need for tanking, then tanking and crowd control can be considered a single commodity and one class will emerge as the preferred vendor for that commodity.

The pressure towards specialization exists regardless of the number of archetypes used. A healing/crowd control hybrid will still have a comparative advantage in a single role unless one or more of the assumptions underlying this economic model is broken.

Summary

The standard model of MMO play fits the comparative advantage theory a little too well for comfort. Specialization is the natural course of the character economy, reducing game complexity and forcing players into a minimal number of tightly constrained roles. Broken hybrids are not an aberration in the class economy, they are the default.

However, this theory is not an inviolable law, but instead relies on a number of fundamental assumptions about the class economy being true for the theory to apply. Clever game design can break those assumptions, lessening or removing the pressure to specialize.

Existing MMOs with successful class economies are already breaking these assumptions, either deliberately or by accident. Hopefully, laying out some of the theory underlying these class dynamics will make hybrid design easier for future MMOs and indirectly make those MMOs more fun for their players.