He was pretty darn overtuned on high tyrannical actually. That DoT was just so punishing, especially with a shaman healer. We literally walked away from him on a 9 tyrannical last week but we had no problem with bosses other people complain about like the Golden Serpent in KR. But Overseer was just constant dots/circles on the same people all the time, knockbacks, constant force to move, etc. We were even using the corner method.