Pick any class and over time and you'll see a lot of nerfs and improvements.

The big problem with same class group composition is that it magnifies the affects of
every nerf or improvement, so a small change that might be an inconvenience to a solo player
makes a big difference to a multiboxer.

I wouldn't even say that the shaman was hit with nerfs anymore than any other class though.
I just think you take more notice of Nerfs to your class than nerfs to others.