I think a good change would be…
Remorseless Winter removed from GCD and damage increased by 100%
Obliteration redesign:
(Passive) Obliterate causes your Frost Strike deal 25% increase damage and grant Killing Machine. stacking 2 times. Frost Strike consumes up to 2 Stacks.
New PVP Talent Remorseless armour
All Melee attacks reflect 35% of the damage taken by the Death Knight as Frost Damage back to the target whilst Remorseless Winter is active.