Chris

The hardest boss we ever fought was G'huun. Even on Normal and Heroic you couldn't mess up the ball throwing and you needed multiple teams to do it because of the debuff. The final phase was a combination of the dance from one of the Naxx bosses and adds spawning on top of trying to kill G'huun. Complete chaos and we only got 1 kill on HC with only 1 man left standing because we couldn't be arsed to go and do it again. We didn't have the manpower to do Mythic though so I don't know how hard it was on that level.