After a late night talk with my friend about healers in XIV, i've come up with what I believe to be a simple and easy fix to a lot of WHM's issues as it is right now. I genuinely believe if the devs incorporates these two things it'll put WHM in a really healthy spot without being too overpowered.
1. Make Afflatus Rapture and Afflatus Solace oGCD's. This gives WHM access to more heals without dropping glares and lets them do burstier heals when you really need it. This also incentivizes using lillies instead of just letting them float by as most people do right now unless they need to move or really need fast heals immediately. This also makes it where the potency of blood lilly doesn't have to be adjusted because dropping them as oGCD's makes each blood lilly a 590 potency gain over Glare 3 instead of a 30 loss as it is rn. This simultaneously gives you more blood lillies per fight because it incentivizes you to use your lillies even if you don't necessarily need the healing in order to keep them growing, unlocking the blood lillies more often for DPS sake. This adds another level of optimization to WHM that was removed after ShB because you would similarly not want to cap on lillies back then as well for the sake of unlocking the blood lilly which was at worst DPS neutral, with the chance to be positive.
2. Make it so that when you use Presence of Mind, every spell costs 0. PoM is easily WHM's biggest MP drain as it is right now and as much of a blessing as it is DPS wise, it reminds me of MNK with Arrow cards back in StB because you just bleed MP SO fast rn when you use PoM. As much as i'm not a huge fan of Thin Air as it is right now, it DOES still have its uses if you're smart about your usage. Even so, on fights like P1S that have pretty much 0 downtime, even if you use Lucid well, WHM still bleeds MP pretty bad, mostly because of how much glare spam you do during PoM windows. This is not an issue that current Thin Air can really prevent, therefore I propose we put old Thin Air's ability on PoM itself, and keep new Thin Air as it is right now for bigger spells like Cure III, Raise, Medica II.
I know this wouldn't fix EVERY little issue that WHM has but I strongly believe with these two changes you could put a quick Band-Aid on the job to put it in a much better spot than it currently is. I should also note that this is only based on my experiences in the current savage raid, so I can't speak on how good these changes would be in past Ultimates or the leveling experience of WHM as it is right now.