I did it the eassy way.
My hero is a shield-wearing warrior specialised in slashing, and my Death Knight is a Two-Handed sword wearing warrior.
They were both lvl 10. I played on tactical.
I killed each Death Knights in 4 or 5 five blows.
They hit hard tough.
But that was not a problem, I just used potions, my warriors were though enough.
As you can see, it's quit unchallenging. I even consider to just stop playing and restart again with a mage/warrior combination.
Knowing my way of playing I would just tank all the death knights on my warrior and blast them with my wizard, using the whirlwind attack a bit and lots of potions ( life for warrior, mana for mage ).
