To clarify, I only play resto if I can help it. Not much of a fan of dps for some reason. I just really enjoy healing...every class is going to have its OP moments and its not so OP moments. During Sunwell in BC resto shams were in very high demand, for alliance especially because Ally had just had shamans become available to them.
Right now the OP healing class is a monk. For 10 mans anyway, they blow every other healer out of the water on non-aoe friendly healing fights especially. But that OP train will end, just like every other OP train has ended and a new class will get to board and enjoy the ride for awhile :P