There is homogenization that is good for the game, and homogenization that is bad for the game.
Consider Blood Lust/Heroism and Rebirth (battle rez). Those are very powerful abilities and probably mandatory for raiding. If shaman and druids were the only classes that brought them still, then every 10-player raid group would need
a shaman and druid to be successful. In a game with 10-player raids and 11 classes, that means someone is excluded. Even worse, if yours is the guild with 2 really good rogues or hunters, you are going to have to make the choice to sit one of those players out in order to be optimal. Even if that hunter is a really nice guy or a good player, he can't come because you need Blood Lust. We don't think that's fun, and we know a lot of players agree. There are several abilities in this mandatory or near-mandatory category: interrupts, raid buffs, dispels and so on. We have no problems spreading those around, or homogenizing
the abilities that mean groups can bring the player they want to.
The other category though is making each class feel a bit different when you play them. These are abilities or mechanics that tend to make your class or spec feel unique, but aren't mandatory. There are a lot of these in the game: Chakra, Cauterize, Bladestorm, Demonic Circle, etc. There are of course still going to be healing, survival, damage and movement abilities in the game that are equivalent in their effect as another classes' ability, but they all work a little differently, and hopefully make you feel different when you group with other characters or play different alts. It's important to us to protect those
differences in the game.