So I have an interesting question for you guys.
First, a bit of history: in my raiding group, we have 4 potential healers: a Paladin, a Druid, a Disc Priest and a Shaman.
Typically, our healing team is the Paladin/Druid/Priest combo. They are all 3 very good healers (with the Priest being a bit behind but still potent).
When we 3-heal with those 3 guys, we do good, but often hit walls.
For a while now, we've noticed a very strange trend: if our Druid isn't there and we replace him by our Shaman, we perform noticably better. This would normally make sense if the Shaman was better than the Druid, but he *REALLY* isn't. If anything, our resto Shaman is very middle of the road, while our Druid is very good. (we did test this - if we put our Resto Shaman instead of the Priest, he is outmatched in every aspect by the Pally/Druid).
What *seems* to happen, to me and my co-tank anyway, is that when our Druid isn't there, the DPSers seem to take much greater care in how they play because they know one of the healers is lacking. They take less damage, use their CDs more, etc.
Has anyone else ever experienced something like that? It's the only explanation I can come up with. The Shaman is clearly sucking - he has really good gear, and is constantly being outhealed by the Paladin and the Druid, and not only that, but he's almost always the first one to die on fights, he has trouble keeping up and is generally an okay player. (He used to be elemental but his DPS was horrible, and he figured mooching to the GL that he would like to heal instead worked. He knew he was going to get kicked from the group, as in full ToT gear he was often pulling a wonderful 40k DPS).