Self sufficient tip to make it easy :
Nightmare mode on easy, remove any gear with pickup range.
I removed most of my legendaries, including pants, helm, gloves and boots. I pretty much did it naked bar weapons.
Now, real easy and simple. Use skills and meeee attacks, but after every melee swing, just roll away from diablo or the clones and you won't get the health orb.
I still killed him real quick, and had rend with the healing rune just in case (wasn't needed).
Basically, melee then roll, melee then roll etc. as the boss is only low level if your 60, makes it a cakewalk!