Is it okay for a healer to pull mobs in a raid/dungeon with an ability that heals and damages?

Last week, my FC & I were doing Orbonne. An AST set Earthly Star in the midst of a group of mobs before anyone had pulled. It eventually went off before the tanks pulled, causing the mobs to attack.

Being an AST main, I disagreed with the AST setting it before the fight began, since it could (and did) pull mobs before tanks were ready. My raid leader, also a healer main, said it was excusable, since it was in anticipation of healing a tank.

I’d like some opinions from other players of varying roles and raid experience. What is your opinion on the matter? No matter your stance, please try to be respectful of everyone else here. Thank you! ^.^