so far what I've tested:
Serpentshrine Cavern (Raid, Zangarmarsh) CLOSED
Shadow Labyrinth (Dungeon, Terokkar) CLOSED
Hellfire Ramparts (Dungeon,Hellfire Peninsula) OPEN but some mobs (scryer somethings) are not 'targetable' by normal spells and can only be killed by "damage on hit" mechanics such as ret aura, molten armor, thorns, lightning shield

