I used unrelenting force to damage him from a fall, then I moved the duel back to a position where he was on a hill above me. This prompted him to get his bow out (which is easier to deal with than his ridiculous one handed damage), I then blasted him with thunderbolts before once again using unrelenting force to make him fall in front me. Whilst he was weakened and getting up, I finished him off with all the magic I had. Took me nearly three tries.

Simply incredible loot from the hardest enemy I've ever fought. Nice addition, Bethesda.

Tell me your stories! How did you deal with him?

I'm PC user so...
Anyway I think Vampiric Grip or Corpse Curse will help to deal with him.

He's a level beyond anything you've ever fought. His health regen. is ridiculous too. He has a shout which paralyses and each blow of his sword is crushing. Distance seems the most viable option so far, haven't tried with a warrior character yet.

Sounds very intriguing.