I barely play, maybe only a few hours a week, but I subbed in a enhance shaman about 4 weeks ago and I'm enjoying it quite a bit. His overall dps is better than the rets I think and contributes a lot to the group.

So the comp is Blood DK tank, 3 ret, 1 enh shaman. I'm slowly levelnig up a warrior to replace another ret, if I feel like it.

This is strictly pve though, I haven't even tried or put thought into how it'd work in PVP.