I think most of you make this fight way harder than it is. The puddles do not do enough damage that they require moving out of. Simply spread your guys out a bit, and put their backs against the wall opposite the boss. I'm not sure how you have your druids set up, but speccing one into wild growth makes this fight a joke. Alternatively, having the druids simply rotate tranquility through the two elemental phases would be more than enough. (have two cast it during the first phase and 2 during the second phase)

My group:
Prot Pally
Resto Druid
2 X arcane mage
elemental shaman

I don't even bother with nature resist totem here. I simply put wild growth into my normal healing rotation so that my druid casts it whenever it is up. That alone keeps all of my guys alive. Perhaps if your guys have a bit of a problem with gear, that plus rejuv would be more than enough. Don't bother moving them - just heal through the puddles. Non-stop DPS and ensure that you smack the elemental the moment it gets spit out.