During fighting Halescourge boss he teleported outside boss fight area, then he teleported back on a platform. After that he disappeared (teleported out of bonds?) and game assumed that he is dead though he had more than 2/3 of health. Right near the exit path from boss area there was another but simple Blight-Stormer-wizard.
May be these two wizards (Boss and simple one) were present at the same time and their parameters were messed up during teleports?
The moment were Boss is out of arena is in the picture