I'm wondering, what race is best for this combo. I have some Human DKs and some Worgen DKs left over from Wrath I could level up, or I could just use boosts, get to 390 ilvl right away. And if I'm going to use boosts, any race would work.

Worgen get a speed boost, that could make dungeon runs quicker, and help move out of gunk on the ground.
Dwarves get stoneform, which can come in handy for an additional defensive CD. (Dark Iron's version of this seems even better)
Kul Tiran get a stun/knockback, and a free 2% heal, which I feel would be nice passive bonus for boxing.
Draenei get a nice 20% of HP heal, which adds up on tanks
Mechagnome gets a free heal when you get below 20% HP which can help avoid wipes, but I feel like getting that low is dangerous enough.

I'm stuck between Kul Tiran and Dark Iron.