We've gotten the challenge in Webs but that was back before the graphical glitches on the floor so you can't see the path clearly now. It's possible they decreased the timer somewhere along the line also because it seems to me it was longer at launch.
This instance has been perpetually messed up, first it wouldn't spawn the challenge chest, then it spawned the chest but it would fall through the floor, and now you can't see the floor when you're out on it. Unless they've fixed the floor in the last patch or two?
Groups we've completed with:
It's all to clear we are on our own.[/CENTER]