Is this the escort quest that happens in discord? If so this is how we beat it (after dicking around with it for a few hours):
We ended up killing like, 10-20 mobs I think, and we tried keeping both mezzed and killing them back to back really fast, but it didnt work. We also noticed that the mobs kept spawning no matter what, which seems like a bug. So basically, what we did was pull mobs into the hallway for a while, killed a bunch (8 is probably enough based on what i've heard from the post on beta boards), and we then kept one alive.
On the last wave before we were successful, we pulled it in, killed the first one...and then knocked the second one down to 10%. Then I knocked it down to 1-2% ish using just auto attack.
Then, you have to wait until no mobs are up to kill AND hail the npc sitting in the middle of the room. If you watch your map you can see when they spawn and despawn...there was a 2-3 second window when we did it. Its fucking stupid if you ask me, and fucking broken, but it worked. We waited until the mobs in the current wave despawned at which point we had a ranger sitting in the middle of the room invis...he dropped invis and started spam hailing as I killed the last mob with 1 special attack.
We managed to get the update and stop the spawns.
If they nerfed this...then uh, they probably nerfed the only way to beat it...seeing how the fucking thing never worked to begin with. I was told the dev got it to work for him, but i think that fucknut was using his little dandy /kill command which obviously isn't going to emulate player dps/group make-ups.
This task and that other escort in bloodfields make me want to stab soe....as they're both broken to fucking hell.