The core issue with Healers is variety, not balance.

[Levy9]

The reason imbalance is undesirable is because it stifles variety. If one job feels significantly weaker than another, that job will be used less often at high levels of play.

Players feel like they have less viable options available for their preferred style of play if a job is underpowered. It's as if that job becomes delegitmized in a sense, reducing variety. When addressing balance, we should be asking ourselves, why imbalance is a negative thing to begin with. What harm does it cause, specifically? The suppression of variety is the answer I come up with. This is also why the current healer problem can't be fixed by looking at it solely as a balance issue.

When SE tries to restore balance by making all healers very similar, we start to see more and more complaints about healers feeling the same or not having an identity. It's because the core issue wasn't necessarily balance, it was variety. The problem was that imbalance was impacting variety and players felt as if they had fewer viable options. When we examine the 3 healers in FFXIV, you'll notice that all three have the same core set of healer GCDs. The AST/WHM similarity is especially notable. Even the basic healer spell animations between the Healers are very similar.

AST Essential Diginity looks just like SCH Lustrate to me. WHM Medica looks very similar to AST Helios or SCH Indomitability. Not only do you have a core healing set that feels the same, it also looks the same to boot. Generally, the biggest differences in spell effects between healers is in their DPS spells, albeit AST does bring some visual flavor when it comes to it's card and star based abilities.

I just hope that SE doesn't see this as merely a balance issue that can be fixed by adjusting some potencies, adding a few abilities or making the healers feel even more similar to balance them out. That would only exacerbate the current problem, imo.

[Risvertasashi]

Well that's exactly part of the problem. AST's core healing is a clone of WHM's spells and SE has said they're not going to change this multiple times. So this leaves essentially 2 possible states:
1. AST is a weaker healer with raid utility, but is underutilized because of the weaker heals.
2. AST is an equivalent or stronger healer but also has raid utility, so no one wants to take WHM when it's simply worse. (as in the latter parts of HW and SB)

SCH is much more complex to unravel. For one you're kinda wrong, SCH doesn't have the same GCD spellset like AST and WHM do. Even in your own example, Indom - while very good - is an oGCD cooldown rather than a GCD spell and that's rather significant. And of course we haven't even touched the pet yet, which is what most people would say is most responsible for SCH being unbalanced.

I will say that scholar feels more like an expac job than AST does, despite it being part of the ARR launch lineup. On the one hand SCH has the most egregious balance issues, on the other hand, if they made the SCH fairy into a healer-bahamut kind of mechanic or otherwise downplayed its role, I will be kinda sad about that too. But it's not like SE is willing to explore the many healer mechanics not yet seen in FF14, so here we are...

[Levy9]

Yes, Scholar is the more varied of the three healers but the point of them having similar cores still stands, just to varying degrees. My Indom example was for spell effects, not gameplay mechanics but Succor - SCH's Medica equivalent - also looks like Medica, but with a brief bubble effect on the players afterwards.

It's as if Medica was the vanilla AoE heal animation, and both of the other healers were given that same floating Halo AoE heal animation but with something tacked on like stars or bubbles. A lot of the single target heals look very similar to me too.

Weak single target GCD (Physick - Cure 1 - Benefic)
Strong single target GCD (Adloquium - Cure 2 - Benefic 2)
Strong Aoe GCD (Succor - Medica 2 - Aspected Helios)
Single target oGCD (Lustrate - Tetragrammaton - Essential dignity)

(Take into account that these spells all have the same cast time relative to each other.)

Outside of this, SCH branches out and does more of it's own thing, whereas AST continues to be a near perfect copy of WHM with a handful of extra healing spells swapped out for card utility.

If WHM gets more utility as a balance change and AST gets more healing instead, these two classes will essentially be the same class. A rework seems very necessary at this point.

[Nathanial]

Everyone brings up pets but its like no one has actually tested how much they heal for.
What ever pet skill potency says it is, you have to divide it in half. If you literally cast a pet skill that is suppose to have a potency close to that of a spell form an actual player, you will see it literally heals half on that amount. for example, embrace is 250 potency and adlo is 300 potency. when you heal a target with these comparable potentiates the embrace heals for less than half the amount its potency would lead you to believe. My adlo heals for 5000 at 300 potency, my pet heals for 2300 with a potency of 250. if you have a hard time with math 300-250=50 potency difference. but 5000-2300 does not = 50 potency difference. thats literally 50% lower than it should be.

[Risvertasashi]

Everyone brings up pets but its like no one has actually tested how much they heal for.
What ever pet skill potency says it is, you have to divide it in half. If you literally cast a pet skill that is suppose to have a potency close to that of a spell form an actual player, you will see it literally heals half on that amount. for example, embrace is 250 potency and adlo is 300 potency. when you heal a target with these comparable potentiates the embrace heals for less than half the amount its potency would lead you to believe. My adlo heals for 5000 at 300 potency, my pet heals for 2300 with a potency of 250. if you have a hard time with math 300-250=50 potency difference. but 5000-2300 does not = 50 potency difference. thats literally 50% lower than it should be.

You're incorrect - it's a 2/3rd modifier, not 1/2. In any case, 480 potency is the most powerful regen effect in the game, even after 2/3rd * 480 = 320. WD is still strong. Embrace is still strong because it's a stronger-than-regen regen that never takes a GCD nor MP and just happens, etc.