Art of Defense mode

Maybe as a league, or maybe a quest or vendor, but basically you have a small area you and party members must fight off waves of enemies in. Drops are altered, whether it be to limit drops to cheaper "merchant trade items" or simply to decrease the drop rate of minions to have more minions with less health to balance drops/minute.

Anyways I would love to hang out with 'x' number of buddies killing wave after wave without having to go through the endless dungeon-ness.

Hmm, so sort of like a minigame? That would be a pretty sweet special event. Maybe they can implement that at the later stages, once the game is live.

AWESOME!

Like Firefight from Halo ODST/Reach

I dig.

This has been suggested several times already. I'm sure if you search you'll find the others threads fairly quickly.