Last year at GDC I was talking to the Wild Shadow Studios guys about traditional classes in fantasy RPGs (ranger, wizard, barbarian, cleric, etc.). Some of our complaints about classes in many multiplayer RPGs:
Classes come with roles such as “tank”, “healer”, “ranged”, “melee”, “crowd control”, etc. If you want to join a group that needs a tank, but your class is about melee damage, you can't join the group.
The beginning of the game is a bad time to choose a class, which impacts you for the entire game. It's too early in the game to know what style of play you might like or what kind of roles are needed/useful. By the time you can make this decision it's too late; you've already invested lots of time into the game. Either you throw all that away or you keep playing the class that's not best for you.
Every class's play style can be considered “content”, and by choosing just one the player is missing out on other styles of play. As a game developer, if you have 5 classes, and players only play one of these on average, you're spending a lot of money on “content” that most players won't see, especially if armor/weapons are written for just a few classes in mind.
In Diablo 2, you picked a class but you could also customize that class by choosing skills as you level up. For example, Barbarians could choose skills such as Taunt or Double Swing. The skills had level requirements and prerequisites; for example, Double Swing was only available if you already had Bash. The trees were divided into three specialties per class; each of these effectively acts as a sub-class, so you had 15 styles of play instead of just 5 classes. The skills available to you were fairly limited at the beginning of the game, so you're not overwhelmed, and you don't have to make your choices at the beginning. This partially addresses complaint #2.
In Guild Wars and Titan Quest, you get to pick two classes. Multiclassing has been around since the D&D days, but these two games makes two classes the default and one class an option. Multiple classes can help with complaint #1, since everyone has two roles. It also helps with complaint #3, by adding lots of variety without having to create new content around it.
In Silverfall, World of Warcraft, and Titan Quest, I can change my skills later in the game, but not my class. WoW also has hybrid classes such as druid and shaman that can perform multiple roles. This also helps slightly with complaint #1, but it's quite a hassle. (Recently, WoW introduced “dual specs”, which help quite a bit by letting you set up two sets of skills that can be swapped with one button.) Being able to change my skills later greatly increased my desire to experiment. In Diablo 2, I would pick skills based on the recommendations of others. Decisions you can't change are more likely to be conservative. But in WoW, I am much more willing to try out new things, because I can undo them.
In Dungeon Siege II, there are skill trees but no classes. You essentially define your class by choosing skills along the way, but you don't have to decide anything at the beginning of the game. Titan Quest also delays the decision-making of your first and second classes. Either approach addresses complaint #2.
Another way to address all three complaints is to have more than one character, each one trying out a different class and play style. But when playing these characters, you start over from scratch.
What I'd like is (a) delaying decisions about classes/skills, and (b) allowing trying out other choices after I'm “finished” with my current class. So here's the idea: as you progress in the game, you are given choices of specialties. If you later master multiple specialties, you can become a generalist. Here's a diagram:
After you've played for a short time, you get to choose weaponry or magic. I choose weaponry. After playing more and leveling up with weaponry skills, I am able to specialize again, and I learn melee. After learning all the melee skills, I specialize in swords. After a few more levels, I am now fully specialized by mastering swords, and there's no more for me to learn. This is the equivalent of “level 80” in WoW.
At this point, it's time to try the branches I hadn't tried. This could either be by starting over with a new character at the novice level; or it could be by restoring a previous savegame where I was still at weaponry (playing a “clone” in a scifi setting), and choosing the ranged path instead; or it could be by using my current character to go back and learn ranged attacks. I don't know which of those approaches would be best for a game. In any case, I'm now trying out other play styles, just as with current RPGs.
Where this design differs is that there's something gained in-game by learning multiple specialties. This is the lower half of the diagram. If I master both the sword and axe, that unlocks the halberd. If I master both ice and death magic, it unlocks wizardry skills. By playing and mastering all types of characters, I become a Master.
An open question is how you handle the huge number of skills once you've pursued multiple paths. Titan Quest and Guild Wars limit your classes to two, so that it's not too bad. WoW lets you have two sets of skills, and you can swap back and forth at any time. Guild Wars further gives you a fixed number of skills at any time, and you can swap these out when you're in a major city. In a scifi setting, such as a robot or spaceship based game, you could assign the skills to the robot/vehicle you're in, and then jump into a different robot/vehicle to swap skills (Wild Shadow Studios is working on a tank-based MMO that does this). Choosing sets of skills before you go into combat seems like a reasonable way to limit the complexity, and also encourage planning ahead.
This skill graph addresses complaint #2: you don't have to make permanent choices at all, and the choices you make come after you've been playing the game for a bit. It also addresses #3: there's a path for the player to experience all the “content” the developers create. It partially addresses #1, by allowing you to play different roles at different times. Novice players can follow a recommended path to specialize in just one “class”, whereas experienced players can experiment more and try out new combinations. I think it could be fun to play with such a system, but I'm not planning to write an RPG any time soon.