Your fairy can die while AST healing like WHM is tied to the player and if your fairy dies your HPS drops by a lot and spamming Lustrate does effect your mp regen as you no longer have charges left to help your mp regen what AST has is cards the ability to make all their heals instant cast on the move with light speed and the ability to heal 2 people at once no matter the distance making AST the most mobile healer in the game.