We killed everything in the dungeon, including the optionals and then proceeded toward the end fight.
When we got to the end fight as soon as the boss spawned the dungeon alert started climbing and went right up to red. We did not try to run around or anything. We just started beating on the boss. Once we got to red the whole dungeon lagged up and we died. After we died we both saw numbers for about 10 seconds. It took less than 30 seconds to get to red and maybe another 15 seconds to lag out to playable/dead.
Anyone else had this? Is the dungeon alert set wrong in this quest? Or did we just have bad luck / lag and an unfortuanate time?