I had the same problem as you. i'm was running my dk with 3 elem shamans and holy pally.Just clear my first heroic after i switch to Blood after using unholy and frost in my duel spec.Unholy i was seeing my best results with my spamable macro without the macro stalling.But i was just not getting it done.Respec to blood ,add the dnd glygh i think it 20% add damage was holding aggro better than anything i seen from the other specs and the extra healing from the blood spec was put me well over the top of living thru the boss fights.i did a lot of reading and the spec i went with said not to spec for the blood worms, if that help any to you.Good luck