Hmmmm....This quest can be very difficult for a lvl 84 and yet there are few comments on how to actually get the job done.
I had completed about 10 quests in Twilight Highlands with my 84 DK when I came across this one. It was much more difficult than any I had done there before.
I got killed a few times trying to figure the thing out. I gave up on that and came back with my 85 Pally who hadn't done the quest and learned "the ropes" without getting killed.
First of all, do the quest in the south-eastern part of the area where the mobs appear. There are fewer mobs roaming around, and almost no Worgs. A major problem with the quest, if you do it in the northern part of the area, is that many groups of mobs are patrolling and will agro quick. So will the Worgs.
As was mentioned previously, the second major problem is the rupture in the ground that can hit you with something like 15k damage. When you see the brown dirt start to fly, get out of the way IMMEDIATELY. It may take some practice to avoid the rupture.
I followed a suggestion I found on another part of this site-when you see the brown dirt, charge the mob, get behind him, turn around and continue the attack. Move around as much as possible. Just don't be there when the rupture rises!
If you are a DK, stay away from the mob as much as possible. Hit him with ranged stuff like icy touch and keep infusing your ghoul with death coil if you can . The ghoul will most likely knock him down even before dark transformation procs. In other words, don't start the attack by pulling with death grip. Use icy touch and the ghoul will go to the mob-you don't want him coming to you. Play it right and you can stand back and watch.
The same thing would apply to other classes that have pets., etc., such as the hunter. The mob will stick with the pet and leave you alone in most cases. Ranged weapons and kiting will also help a great deal in this one-anything to keep the mob and the ruptures away from you.
If you happen to get hit by the rupture, you take big damage and your frame rate will slow down, at least on a computer like mine, which is not the latest or greatest. This makes things abit more difficult also. Nonetheless, keeping out of the rupture and away from other mobs are what matter in this one.
Oh, and one last item. Be careful as you are flying around looking over the situation. The Shaman of the Black will blast your mount or flying machine with a bolt that hits for about 5k! They will do the same thing while you are fighting on the ground. There is a quest to kill some of these nasty dudes, do it while doing this one. If you see yourself taking damage from big blue balls that burst around you, a shaman is at work. You may not even see him at first. If he starts throwing the blue bolts, try to get him in melee range where he can't use 'em as well.
All together, this quest was a royal pain in the arse!