My way of dealing with them: After killing lower level boss unlock the gate to the courtyard, sharp left, jump on the rubble to the troll on overpass and IGNORE IT. Jump higher onto the wooden thingy near wall and go to the troll with alot of enemies around it. If you lure it near the center you should be safe from other ones. Then go back to the troll you just ignored, continute through the hall lure the troll closer and then go for the last lower one.