The Second Phase - Dominus Ascendant

Well, melees have a real problem with the first phase ... which you don't.
But that may come from the memory leak causing machine lags tbh, if you can't fully dodge between melee hits = you are basically screwed.

For the second phase, I guess that you can still use decoys ( sum skeletons + spell totem ) and what has already been said ( frost wall/blind ). Maybe you can try to knockback him to keep him out of range too, there are many thing that can help there, but if you just want to auto-hit him, of course you're gonna be in trouble.