Healing needs an overhaul, but this is more like throwing some new paint on a house with crumbling walls.

WHM is not in a good place balance wise nor gameplay wise. The lily system is a nice change of pace, but the job needs to bring the lilies down to early levels and expand on the system to make your GCD usage more evenly balanced between a slightly more developed rotation and utilizing lilies that reward you with bursty DPS refunds. The job also needs to have an answer to mitigation. If we want the pure vs barrier healer dynamic to survive, then sure its mitigation can be limited or come at an opportunity cost, but it simply doesn't have an answer to how damage is foundationally being handled in higher levels of content.

SCH needs a rework. It's confusing for new players to go from ACN to SCH, and the kit is bloated and at war with itself. It also should return to having a DoT focused DPS rotation like it once did, restoring tools like Miasma and Shadowflare, and its resources need to be reworked. The Fey Gauge is a disgrace to gauge mechanics and why does a job need 2 different resources for healing? Why not make the Fey Gauge your healing gauge and turn Aetherflow into your offensive gauge?

SGE is not a DPS healer and it should have a massive expansion of offensive tools or merging supportive tools with new offensive ones. It should feel like the GNB of the healers otherwise what was the point of advertising it as the DPS healer if it's going to play identically to every other healer?

AST is already known to be receiving an overhaul, to whatever extent the devs have planned. I've said it before, but I'd like to see its cards become GCD, its casting focus transition to support, and have the cards additionally generate passive, Malefic-potency damage through a new gauge mechanic. This gives thou-shall-not-DPS healers a job that may still need to maintain Combust and throw a few DPS buttons out once in a while, but can redirect a lot of their focus to spreading buffs.