If a tank loses aggro, whose fault is it?

[AmalonStar]

Depends. If you've got a new gladiator in low level content who's doing his job the best he can, it's on the DPS. Every other situation in this game is on the tank because it's pretty simple to get a good aggro lead

The instance that the OP was inquiring about was a higher lv dungeon where everything gets aoe'd the tank needs to use their aoe enmity ablilities to hold aggro on everything, the tank in that party wasn't using those abilities.

But yes in lower lv dungeons the dps need to watch their dps and make sure they're attacking the same mob as the tank. Although if the tank is good even in the lower lv dungeons it doesn't matter what the dps attacks the tank will hold aggro.