For those who think Avatar will win, it might, but once the MK does Avatar I think it has only 270 mana left. Add in Mana Burn if it slots in before transforming and seriously, you can probably Bolt once or twice before being sucked out of mana.
However, while the MK deals extra damage the DH has the highest Armor in the end: 9 compared to 6 with the MK. And technically, with Evasion, it'll last 30% longer (technically anyway) so its HP is 30% (technically) increased.
Add in the Chaos damage and w00t you have a winner.