Thanks for the guide. We tried this encounter for a while this weekend and found it very tough, although a bit random. Best attempts (with 2 healers) we would get the first Mark at 50-55% and worst attempt 70-75%, with no real reason we could see for the disparity in timing. Additionally, a mark on a clothie was a real issue as the damage got quite huge sometimes.
We did wonder if anyone has succesfully tried a 3 healer set-up and if the DPS managed to get the kill before the enrage.