It isn't that he was nerfed. Now that we overgear him by quite a bit, the idea is you can zerg him faster than the dragons land. Remember that Sarth got buffed by the dragons in various ways including persistant auras and buffs from when they die. By DPS'ing him down fast enough, all you have to worry about is the persistent auras for the first dragon being up and the Enrage. If you can survive the enrage and DPS quickly, the other two dragons don't come into play and he can be taken down before he becomes dangerous to the tank.