Eh I think that all depends on how well the multi classing system works in my opinion. But then again, maybe you're right...
My only worry so far, is that while each class will have it's own unique powers and abilities... they'll all be "the same," just with different colored paint.
By that I mean, if every character gets an ability styled out like the paladin smites... What's really the difference aside from the type of powers, and flavor of said powers?
Green fire ball, red fire ball, purple fire ball... in the end they all do 1d6/level*