One of the interesting things I've noticed in the design of several upcoming MMOs is that several seem to be moving away from the traditional "character class" game mechanic. Once upon a time, each character picked a class, which could not be changed, and that choice defined their role.
This approach has drawbacks. One of the most frustrating aspects of traditional MMOs is finding a group of players to play with that fill all the requisite roles. Its quite common to see people with almost full groups, unable to continue, shouting that they are looking for a tank, healer, or mezzer, over and over again, until they find one. This results in a lot of sitting around, not playing the game, just because you need ONE more person on a server with thousands of people on it and the group can't work without them.
In DC Universe Online, each powerset comes with three modes: offensive, defensive, or utility. You can change your role depending on your mood, what you want to do, and what is needed. The Agency likewise has a "you are what you wear" system of defining roles, meaning you can similarly change your role depending on what people need at the time.
Brilliant! Swapping out the "class" mechanic for "stances" removes one of the major impediments in grouping. Removing the types of obstacles that make grouping a pain is a great step forward for the genre.