Possibly related, after exiting the game AMD CCC notified me that there was a problem and it lowered display settings. My monitor was set from 120 Hz to 60 Hz. Upon restarting Win8, I get the same notification but my second monitor didn't detect. I'll post whatever workaround I get. Could be AMD's fault, I've seen this problem in Windows 8 before.
Updates:
1. 120 Hz: Had to disconnect my second monitor AND restart to get this to stabilize. Kept getting popups about display port failures, lowered settings, blah.
2. Disabling crossfire dramatically improved performance in this second part of the Cathedral. It seems to be running mostly near 120 fps, but with frame latency issues causing it to be bursty. I don't remember it being this bad prior to this level with crossfire, so either it's because I've lost performance from CF or this level is just grossly inefficient in some area.