I have found the spec I use is the most common with a tweak here and there, I juggled some points over to unholy cause I like the extra disease uptime but that's a matter of style I guess. The World of Warcraft Armory
I'm using variations on 12/54/5. There are certainly a few points with room to be moved for utility; temporarily, I've dropped a point from killing machine to pick up hungering cold. This spec revolves around a single-disease rotation using Howling Blast as the sole method of disease application. It's extremely strong for quick start-up threat, looser on GCD's, and pulls respectable sustained threat - the only weakness in threat is picking up continuously spawning entities such as the worms in the Hodir trash.
As this is a frost spec, it's worth noting unbreakable armor has several situations in which it may not be capable of performing as needed. Keep a blood or unholy offspec available and be aware of the needs created by the encounter you're up against, and change specs prior if needed.