Trying to balance the 3 healers is not simple because they not fulfill the same role in the party. We always need a regen and a shield to do a progression in the game so we have two “types” of healer.
We kinda face the same problem with the tanks, but they fix it adding the Gunbreaker. Now tanks have 2 MT and will have 2 OT. Making everything easy and more simple to balance.

On the healer side we have a “main healer” (Whm), an “off helaer” (Sch) and a hybrid (Ast). For me they should move the Ast to the “off healer” side and add another “main healer”. Don’t need to kill the diurnal stance, just need to make the nocturnal more strong and pair with the Sch. Or they can do the oposit but will be harder since whm don’t have any type of party shield anymore. (Rip Stoneskin)

I really hope they recognize that and add another healer ASAP.