I just put up a video on how I do this guy. It should be even easier for you with 4x shamans. Just arrange you team spread out how I do or any other way you prefer and use 4x healing stream and a nature resist totem. Make sure you move your tank away soon as he disperses and when he come back together so you dont eat all of the sparks at the same time.

Heroic HoL Ionar easy tank and spank method