They should focus less on balance and more on fun.
People are always going to whinge, always going to try and blame their own shortcomings on something else (like overpowered specs or unfriendly fights for their class) but in the end, homogenizing and making everything perfectly balanced simply never works.
Even now that classes are at most a couple percentages behind one-another, we have players going "THIS SPEC IS USELESS!!!"... Just, give it a rest, make classes fun again.
Reroll the classes to MoP and we're golden!