Went through the entire quest and was about 5% away from killing the boss in this quest when he mass feared and caused me to run off the map and bugged the quest. This boss is standing right on the edge of a cliff AND the instance boundary, and I cannot kite him away from it either, due to the NPCs holding him there and him being ranged.
Seems like a bit of a poor set up, but wanted to let the devs know so it could save people a headache in the future.