Yup, that's right - our ten man achievement run finally did it! After weeks and weeks of figuring out how to coordinate the heals on infest, work out the timing on horrors, burn down raging spirits, move out of defile, heal through/mitigate Soul Reaper, snare Val'kyrs, avoid/take (depending) vile spirits, and rock out in the LK's Frostmourne, we FINALLY did it. 10 man, no buff, clean kill. Not only that, but it was the first attempt of the entire night. We totally rocked it. =)
Onto heroic mode!