It is recommended that at least five players who are level 66 or higher try to take him on. He does a 10-yard AOE knock-back. Generally, his hits cause 1000-2000 damage for plate wearers, 2000-3000 damage for mail wearers, 2500-3500 damage for leather wearers, and 3000-4000 damage for cloth wearers. Thus, it is of paramount importance for cloth wearers to stay as far away from Durn as possible and still be within the maximum range of their spells.
The quest to kill Durn exists for both Alliance and Horde players; Alliance players receive it from the "Wanted: Durn the Hungerer" signboard in Telaar, and Horde players can get it from Warden Bullrok in Garadar.
Durn wanders in a circular pattern around the Spirit Fields that surround Oshu'Gun in southwestern Nagrand. It is possible to wait at the area south of the Consortium camp and then tag him. Kiting is no longer possible since patch 2.1 He moves fast and is immune to any sort of crowd control, root, or snare.
Durn hits very, very hard, roughly equivalent to the second-to-last encounter in the Ring of Blood event. Though the quest and Durn are marked level 67, at that level two healers and a full group of 5 are pretty much required. Durn has roughly 120,000 health. He also has a wide area point blank AoE which deals damage and knocks back. A well-geared threesome (or maybe duo) of level 70 players could probably take him down.
For warlocks, bringing along an enslaved Felguard Legionnaire significantly helps with this encounter, as well as many of the other group quests in Nagrand. As of patch 3, a level 70+ demonology warlock can solo Durn with little effort, through the use of a Felguard and Improved Health Funnel.
It is also possible to solo him with a well-equipped protection warrior with moderate block values.
He can also be soloed by arcane mages with good use of Slow (Mage spell) and instant spells.