There's been some discussion recently on the Blizzard forums, WoW Insider, and Twitter about class roles.
The point that most concerns me about roles is this: "Hybrid tax."
Here's my definition of it: The hybrid tax means that if you play a hybrid class (one able to peform multiple roles), you give up a degree of effectiveness at a particular role in exchange for being able to perform another role. For example, a paladin's DPS would be "taxed" and not be as good as a rogue's, because the paladin is a hybrid class: able to DPS, heal, and tank, whereas the rogue can only DPS. To make up for this discrepancy in available roles (and thus utility in the game at large), the paladin's DPS is artificially suppressed, or the rogue's is boosted, depending on your perspective, to ensure the rogue has a place, a reason to be brought along.
They're both melee classes, and they're both operating in the DPS role. What's the difference? It's that if the paladin and rogue are both able to perform as well in the same role, there's "no reason" for someone to pick rogue, they might as well pick paladin and be able to do more than one thing and be invited to more things.
Why relegate yourself to just one thing and not get invited if you don't have to? The why is the benefit of the tax—you get more out of your role by being dedicated at it. Pick a rogue over a paladin because the rogue will do better at his role, DPSing.
I support the hybrid tax because of how things are now.
I would prefer that every class be able to perform multiple roles. Everyone should be hybrid, no one should be dedicated. This would eliminate the tax altogether and everything would be hunky-dory, leaving us to quibble over whether druids or priests should heal better, or whether melee or ranged should have higher DPS.
You know, the important topics.
But that's not how things are. Instead, there are classes that are only able to perform one role. Nearest to my heart is of course the mage, who can only DPS. Others include the hunter, rogue, and warlock who, also, can only DPS.
While it's not unfair that these classes cannot also perform other roles, I think the game would be better if they could. I would love to explore being able to heal with my mage (one explanation I like is that mages would heal by turning back time on people to a point before they were injured, using chronomancy spells—a theme that's already going to be supported when Mists of Pandaria releases that includes chronomancy talents).
I think it's critical to clarify what a "role" is and isn't, and thus whether your character is a hybrid class or not. There's a simple test:
If you have the option to select more than one role in the dungeon finder, your character is a hybrid class.
That's pretty much it right there. I believe that being able to perform a limited function in a particular battle does not constitute a role. For example, being able to stun someone in combat, or remove oneself from danger, is not a role. It can be a valuable trick, and depending on the fight and the makeup of the group it can be just about vital, depending on how things shake out in that situation. Again using mages as an example, being able to cast Polymorph is not a role because not only is it only rarely used it's not usable all the time, even if it was called upon.
Tricks during particular fights is far too limited a scope to rise to the level of importance as an entire class role.
What do I want?
I want multiple roles for everyone, for every class to have the opportunity to do more than one thing so the idea of a hybrid tax is ridiculous. Warlocks should DPS and use their demons to tank. Same as with hunters. Mages should DPS and heal, as described. There's no reason to expand even on that, having mages tank by summoning elementals, or warlocks heal by transfusing demon-boosted blood.
Is the hybrid tax unfair? I think it is to those who have to pay it. I think it's not to those who get the benefit from it—but would be if it was taken away. It's a question of where the unfairness should be placed: onto the classes that have choice or the classes that don't?
Right now, it's on the classes that have choice, and I think that's where the unfairness has to be, given how things are. The hybrid classes are rich enough to pay the tax. The beneficiaries are too poor.
The best solution is to not have the unfairness in the first place. Hybridize all classes. Allow multiple roles for everyone.