Let's talk about vanilla and BC WoW for a sec, back when things weren't balanced at all. Basically back then each class only had one respected spec. If you were any of the other specs you were either laughed at or not taken in parties at all (no dungeon finder existed either, so you had to join other people's parties or form your own in trade chat). My husband played a fury warrior back then. This is basically a dps version of the accepted tank (prot). The class offered good dps, but no crowd control (extremely important in dungeons back then) and ... well, wasn't a tank. So he got overlooked a lot in groups unless I insisted on bringing him with me.

There are tons more examples, but the basic point remains the same: choice doesn't matter if its not balanced properly. Everyone wants to have fun and be included. The only way to do that is either make the content so easy you could do it with a single player or balance everything extremely well.

I love the class system this game has. Its awesome that I'll never have to make an alt. I love being able to do everything on one character. I do not think this game needs specs for each class. Though, if they could balance it, it would be a welcome addition. I don't see it happening though.