I'll guess the spell order will be similar to Mosg2's DK Manifesto.

Specifically:

a) Howling Blast + Frost Strike, often.
b) Necrotic Strike (x4, x1 per DK) as close to every 5 seconds as possible.
c) Blood Strike, for the Death Runes; Blood Tap for the opening.

Mind Freeze, off of the GCD, built into the attack sequence, ideally evenly staggered.
Death Grip on round-robin.

Clicks for: Anti-Magic Shell (Debuff Application), Icebound Fortitude (Stun), Lichborne (Fear), Pillars of Frost (Knockbacks).