I think that what you're hoping for is a pipe dream, tbh. If DNC is the next healer I can predict its kit to the letter minus its job gauge gimmick and "utility". That's not fun. It will have a 400 potency basic heal, a 300 potency AOE heal, a 600 potency bigger ST heal that costs more mana, a 600ish potency ST "oh crap" button, a 200 potency AOE damage spell, a regen or shield ST and AOE spell, some variable number of DoTs, a ST filler nuke around 250-300 potency (to account for SBr healer DPS scaling), a 500 potency oGCD AOE "oh crap" button, an AOE regen or damage reduction ground target bubble, etc.
If you don't design healers to be different from one another every one of them will have this same copycat kit and to me, that's incredibly dull. "Niches" dont mean, "useless everywhere else" - ARR SCH still HAD AOE healing, it just wasn't their specialty. Now though? They just rotate ETactics Succor or Indom every 15 seconds with Whispering Dawn filler and outside of brute force crap like Almagest/Heartless Archangel it's no different from having a WHM in the group, just more GCD efficient with better rDPS so thus just...better.
I get what you're saying - if Indom didn't heal for half of everyone's healthbars having a spammable AOE heal like Medica/Helios/Cure III would have more value. But IMO it still wouldn't change the fact that WHM and AST feel really same-y once you strip AST's card gimmick away, and that even though SCH feels more unique than those two it still has a lot of similar moves, and that tells me that the dev team feels painted into a corner when it comes to healer design. There's no room in this game for a cleave heal specialist (2-target healing), or a single-target channeling healer, or a pure HoT-based healer, because those things wouldn't fit nicely in the prepackaged box of healing spells SE allots for healers every expansion.