The shocktroopers portion of this quest is a good opportunity for bards to practice their pulling techniques. As an 81 bard, I was able to single pull the shocktroopers without clearing any other mobs, albeit with various deaths and do-overs trying to get it right. Here is what finally worked for me:
Set up camp in the safe area north of the messcook area and south of the catapult area, on the east side near the boulder. Position bard to the south of the pit full of goblins and shocktroopers on the west side, just out of agro range of the goblins (large agro range). Pop your eye of zomm from the singing steel helm and use it to pacify all of the shocktroopers, then quickly tag the front goblin. Run the goblins south through the messcook area and fade. Make your way back to the pit and tag one of the shocktroopers, causing all of them and any remaining bystanders to agro. Run them south through the messcook area and fade. At this point, what you have accomplished is putting most of the goblins on a different schedule from the shocktroopers, as regards walking back to the pit. Run back to camp and target the shocktrooper who is farthest behind in walking back to the pit. Mez him and immediately fade. If your timing is right, all the other mobs should now head back to the pit and out of agro range and you can single tag the mezzed shocktrooper.
Rinse and repeat for your 4 shocktroopers.
Maybe more experienced bards can share an easier method. My 3 box group of level 81's had to single pull or at most 2 pull in order to survive, so I needed to figure out this pull in order to finish the quest.
