In-case you guys haven't watched the TED Talk on the Paradox of Choice, I suggest you check it out. (http://www.youtube.com/watch?v=VO6XEQIsCoM)
I think MMOs should go to a core of roles without variation. There should simply be the tank class, healer class, melee DPS, caster DPS, and ranged physical DPS. (Maybe one additional slot for a character type that's basically a buff-bot.)
I also think talent choices should be removed and everything about the classes should be standardized.
True, you give up the choice of some 30-40 play styles that are currently in WOW, but for that you gain 5-6 unique classes that can be perfectly balanced among each other. The tank would have exactly what it needs, the healer would have exactly what it needs, and the DPS could be perfectly balanced against the others.
People would know exactly what they're getting when they make their characters. A healer and tank are group centered roles; you will level slower than dps classes, but you will be in high demand for group content.
I know some of you are altaholics like me, and of course there are some of you who have rocked the same mains for years. Personally, this Paradox of choice really hit home with me. It killed a lot of my fun in WoW when I would gear out one spec, only to realize the options another spec had but with a different gear set. Then when I would exhaust that, I would think about the benefits of another class and reroll. It was a never ending cycle, and I would never just stick to one character. For people like me, which I would argue is much of the population, I think if we removed so much damn choice that the player-base in general would be more happy.
I would rather Blizzard could balance the game in a few hours with limited classes, and then dedicated massive amounts of times to content than I would have them reinvent 40 classes every expansion at the cost of less content to explore and conquer. Think about all the changes in Mists...if Blizzard only had to revamp 5 classes, it could probably have twice the content. The wonderful thing about the content is it's not choices that need to be made, it's conquer everything to win. Not "I didn't do this, and this looks a lot more fun - I've wasted my time."
Just my opinion. I think a more baseline MMO would be more enjoyable. I thought I liked all the choice for years, but in my older years I think I'm realizing I would rather have a polished game where I know I'm the best (character ability wise) tank or healer in the game and that no archetype is better than be in any situation simply by virtue of their class choice.