heal reduction or block buff debuffs will make for a much easier fight, and reducing his max hp might work too although that will take a fair bit of time.

that said, your best strategy against ultimate death knight may be to just not fight him in the first place.

Thx yes its some option. First destroy his friends ;)

Who are your damage dealers?

Returned to this game recently, I have the same problem. Why is he so game breaking? He heals on every turn, when taking dmg, when I heal, sometimes he completely negates my dmg, I do 0 dmg, and most frustrating thing is 10 times in a row I get his health to 0 but he still stays alive, how exactly does he do that? Is there a mastery or item set that has 80% chance not to die, becuase that is quite high.

Bad Idea, that only enhances the Death Knight. If you can afford it, focus him down before you eliminate any of his Teammates. 

But yeah, other than that I avoid him. I barely play Arena anymore. DeathKnight here and there and it's kinda annoying if you don't got the tools. I'll wait until he phases out like Deliana did (you barely see her)