I stayed in the entire 2 1/2 hours it took to finish the event, but at the very end, when it was time to “officially” attack the ancient karka, I died where no one was around to resurrect me, so I had to respawn at the nearest waypoint. By the time I managed to get back to the cave, the karka was dead, and I couldn’t click on the chest.
Even though I did 95% of the last event (and 100% of the other two DEs leading up to it), and even though I’d attacked the karka at various points during the two events where it was active, I got nothing for it, not even karma, cash, or XPs (for the last DE in the chain; I did get those things for the previous two). Since there weren’t drops, I literally lost money doing this event thanks to waypoint spawning a few times.