We still strive to make the classes as unique as possible while offering a balance that doesn't lead to anyone feeling useless in raids (which was a very real concern a few years ago), and to a greater or lesser extent, I think we accomplish that goal. When I play a Guerrero
, Caballero de la Muerte
, or Monje
, for example, there are certainly similarities--they are all melee classes, after all. Crucially, there are also significant differences that span the entire experience of playing each class, and which contribute to a distinctly different feel for each one. Even among "pure" classes, each spec can feel quite distinct from the others, and that's certainly the case amongst hybrids.
So, for fear of using an often tossed buzzword, "homogenization" is a matter of degrees. I personally don't feel that we've at all crossed a threshold where playing one class feels essentially like playing another. I find myself reading posts where players are talking about the buffs a class brings to a raid, or listing off the abilities a class has like a litany. These lists are, themselves, devoid of context though. More classes bring more buffs because that was a problem we needed to solve. Classes have similar abilities to encourage flexibility in group composition. If these are the only measures by which you judge how similar classes are, then I think that you're missing the trees for the forest. Nuance matters. "Feel" matters. How a class toolset interacts with itself matters.
I would make the case that, for the purposes of game play, how a given spec or class plays is really what makes it distinct from the others, even if different classes can sometimes share similar roles. After all, that's nothing new to World of Warcraft; we've always had healers, dps, and tanks. Players have greater flexibility than ever to choose a class that they enjoy playing for the raw experience of playing it, rather than for what buff it provides.
I don't mind so much the same effects on different classes to even out raid need but I do wish that the classes were different enough that just by eying a piece of gear you could tell what class it was meant for even if it wasn't a set. A good example was back in BC when you could tell the difference between Lock oriented gear and Mage oriented gear by the amount of Stamina on it.