The problem with the stuns is that they affect different classes in completely different ways. Any class that can cast a ground-targeted AoE (ex., Death & Decay) is fine, because that will kill the parasites even while the player was stunned, while classes that can't generally end up stunlocked.
Myhtic Gul'dan was soloable at 8.3, i think blizzard wasting they time with legion stuffs we need more content not cosmetics.