That part is easy as well and the same strategy. At that room with the 3 waves you stay at the entrance to the room and kill all the enemies. None of them come through the door. The only ones that will eventually come through the door is the last wave of 3 or so wizards. When they finally do come through the door. High tail it to the previous room and kill them from that entrance. Just make sure you have fire damage (snipers are great for wizards, or vision of confluence). For the Phagoth portion, do what was suggested but you need to make sure you initiate the fight with the boss (when dinkle says good thing hes chained up) or xyor will never come.