In my opinion I prefer imbalance in pvp. Its OP teams and class's that create a challenge, make you change how you play your class so its not so generic. Saying that, fair enough if a group of healers or maybe a group of tanks or nuke groups would be a bit annoying, I would be happy if they simply went back to 1 healer 1 tank 2 DPS (of any kind).
WD pretty much died when they restricted it so much, it was like saying you cant play with your friends any more or play interesting setups. The arena is a strategic for of team based play and limiting it is like saying jump in a boxing ring and have a fight only with one arm tied behind your back...its no fun let us play with both arm's!