I finally beat him, but by sheer luck. Standing in his way, pinning him in with summons, and trying to race him to the switch ... none of them work in DKS, at least the current Steam version. He actually just warps to the open healer. No chance of heading him off, one second he is in front of you fighting, next you get the cut scene of him healing, and nothing in between. I resorted to guessing which healer he would head to, then running there and shutting it off before he tried to use it. Needless to say, I was wrong most of the time and he either went the other way or simply warped to the one that was still on. I eventually got lucky and guessed right twice in a row, which game me the time to finish him. And at level 32 he really ought to have been a pushover. Even the 20 or so summons left over after he died were no real problem, just the unstoppable heals.
I don't care what anyone says, this is simply bad design. There ought to be a strategic way to fight him.
