It has things that make it unique, namely all the CC options...Holy (the only AoE stun in the game), Fluid Aura, Sleep (sadly I forget it's real name). Problem with all those is they are relative non-factors when it comes to raids. AST can cover the same sort of healing as WHM via Diurnal Sect and have all those tasty cards to toss around. Meanwhile, the fairy co-healer does it's thing while it's SCH minion continues to dps.