I'm currently playing double frost dk in arena, both using this CR. It's really good but there's a couple of things needed. Could you make it so that when being attacked, it has conversion up constantly? I auto switch stances and stuff, but it'll be much better dps leaving conversion up than having to keep activating "spam self heals". Also, I kow it may be difficult, but is there any way of adding some logic for dark sim to cast when it's off cooldown straight away, and use what it gets appropriately? If it's cc, cast on your focus. If it's a heal, cast on your or your team mate (depending on health).
Implementing those 2 little things could help get double frost dks to 2.5k+!