On phase 3 I found a better way to go about healing for me. He does a shadow bolt every couple seconds to everyone in the party. So the more people you have the more damage he does. I found out I simply don't have the healing to keep everyone alive so what I do is give priorities to heals and sort of sacrifice a guy. When I was healing my lowest hp character everyone else continued to get hit and pretty soon it would be too much to handle and everyone would die pretty close together.

So now i give heals in this priority...tank,healer,highest dps, 2nd dps, last dps. You might think this is what you do anyway but I only give someone heals if everyone above him is almost topped off. Usually I get through with only 1 dps dying but sometimes 2 will. But the good thing about when someone dies is it make healing on the remaining guys that much easier.