Arrested Development

Arrested Development is a dungeon & raids achievement earned for allowing all three of Corla's zealots to evolve, then defeat Corla after slaying the evolved zealots in Blackrock Caverns on Heroic difficulty.

Strategy
Start the encounter as normal, but let 1 of the adds evolve at the start of the fight and kill it, then release the next and so on. Be sure to interrupt the Shadow Strike Ability or else your tank might get in trouble. It may be useful to use defensive CDs at the first and third add and use offensive cooldowns when the third add is released.