The Spirit Realm

Hrm, hadn't factored in the regen, yea he did used to have a high one. Of course after the rise to 90 that doesn't seem like it's going to be as big of an issue for CoA-era mobs.

iirc, you have to sustain something over like 2.5-3.5k (something in this range dont remember exact # offhand) to pass his dps and be able to kill him

The regen is reset mechanism. Means someone clicked the wall into his room and didn't then immediately agro OMM. He starts jumping 20% at a tick. Someone in the group you describe as "we" very nearly 1-900-MixALot you over completely right there, because if he gets to 100 the script is reset completely re: adds/dts/port/etc.

Ahh, well, 20/20 hindsight. Most of the group I was with had never done the event, ironically the one that made this mistake was one of them that was there for our server-first kill of OMM a few years back.