Sadly, WoW did it right with 3 specs. You spend the first 10 levels as your base class, then you flower gloriously into something new. Every level gives you a point to toss into something that powers you up or gives you an ability.
M&M has very little customization and its kind of painful.
Why explicitly limit people? Give them an avenue to at least tailor their own experience. You dont need to create new classes, but just give us options.
DPS Tank ~ Special stances on a long CD
INT healing ~ bubbles/runes/HP transfer
INT melee DPS ~ Bone Knight (NickHotz)
Evasion Tank ~ Rogue/Monk CDs/special taunts
These mixes by no means need to be on par to something dedicated to 1 role. All they need to do is target specific popular class fantasy and all it costs is a specific item, AA or another layer of customization tied to levels or gods.
I will be sad to read the Fighter update, knowing what they want to do with it but thats OK. There is a lot of good too.