I remember when the fight with Necron took me completely by suprise, but I beat him anyway.. I must have died about 10 times too..

I had Auto-Revive (or something similar, either way I couldnt die), and I literally just wore him down.

I forget how I got that ability, and where, its been waaaayy too long but try and search around for it and get it for as much characters as possible that you are fighting with..