For heroics, I think you'll run into a problem with either 4 split-spec shammies or 4 elemental. You will probably need to break one out and spec him straight restoration due to the damage you'll take there. To better answer this, though, how are those two guys geared? If your war is all geared out the wazoo, you might be able to get by without as much healing and the occasional untalented healing wave x4 might be enough.