This patch will constitute a major buff to Death Knight tanking...
Right now, Pestilence has a 10 second cooldown. Pestilence is required to spread your diseases to multiple targets. If one of your diseases on your original target is resisted or an enemy is out of Pestilence range when you use it, you are either dealing half AOE damage or completely helpless to cause any AOE damage to that enemy, respectively, for ten seconds. This usually results in the particular enemy eating your healer. On top of that, each enemy that does not have Frost Fever will be attacking at its full speed, and when that's 7 of them (like last night in The Nexus,) that can hurt.
In 3.08, Blizzard will be removing the cooldown on Pestilence, greatly reducing the crazy do-or-die timing aspect of Death Knight tanking.