Just did a +8 Tol Dagor, ive done this dungeon plenty of times in the past, and on harder difficulties, and while my group certainly wasn’t great, Overseer Korgus seemed to be casting explosive blast almost continuously. On more than one occasion he cast it literally back to back, as soon as the damage happened on the first one, he cast it again. At one point i got so far away from the boss from the continuous knockbacks that i couldnt heal anymore even though each time id move up as much as my poison bar would allow, not mention trying to keep people up that are continuously taking half their health in damage from an unavoidable source. We wiped twice to him as a result, eventually i just planted myself against a wall and we just barely managed to kill him with 3 battle reses.
Not sure if it was just a random occurrence or what but that definitely shouldn’t be casting that often.