I have a fun story about the Lighthouse. 24-player raids are more fun when players don't know the mechanics going in, thus figuring them out becomes part of the strategy.
Anyway, the first boss we got down to 20% before Alliance wiping.
Second boss was kinda miserable to be a healer since nobody figured out that chains mechanic, but no wipe.
Third boss (the one with the math mechanic), really showed who wasn't paying attention. Or didn't get the math. I felt this was a cool mechanic, but probably should have been more literal. Alliance wipe at 25%, one time.
Fourth boss, someone had the nerve to try vote abandon, twice. The co-healer from my party and two DPS from alliance A dropped out at this point (90 minute mark.) Unfortunately the new co-healer couldn't stay alive more than 5 seconds every time they were raised, so I tried raising the RDM instead, and that was not any more successful. (point of reference I had 38K hp, first co-healer had 42K. Second co healer had 36K.)
By the end of this my gear was down to 17%.