This fight was simple tank and spank, here's how you do it with 5 shaman:
Drop down your totems (In this case, healing stream x4 mana stream x1, grounding totems)
Park your shamans infront of his cave, pull the boss with your main shaman.
He will spawn adds, pretty much just focus on him instead using chain lightning when it's up, chain heal and lightning bolt and flame shock/earthshock, after he spawns a bit too many adds you should stop using chain lightning on him and put down stoneclaw totems and magma totems and just finish him off and then kill the adds after.
I'm not sure what his heal is as I've never encountered it, he seems to die in about 2 sets of lightning bolts and 1 chain lightning (maybe with a shock can't remember) he has super low hp