I know on my 4 shaman I always look to give gear to the toon that is my heal toon first. The regen needs to be higher as well as the mana pool so they can last longer. The elemental shaman x 3 aren't an issue as they just work well together but your healer needs to have the ability to last for a semi-long boss fight. They are all in Brutal gear but when I go into an instance the resto puts on the spirit gear and there we go.