Since the advent of 6.0, people have seen a few changes to WHM that have helped it in some cases; however, there are a few glaring issues that are causing WHM to underperform in both Savage and Dungeons as early as Sastasha:
Thin Air Charges - The Thin Air change to Charges wiped out 4 GCDs worth of healing that we could've done from Shadowbringers and Stormblood, ripping out a gigantic chunk of our MP management kit. WHM has not gotten any recompense in regards to MP since then, making it difficult to manage when simply casting Stone in low level dungeons, thus reinforcing a bad habit to sit there and only heal like Sylphie.
The Change to 1.5s GCD - While the change to 1.5s GCD is helpful to WHM, it is also a detriment due to their current systems in place - namely Lilies. The Lily System that WHM has forces GCD healing, causing Afflatus Misery to be a loss a majority of the time and ALWAYS a loss in Raids. One of the biggest issues right now is that WHM isn't contributing as much as it should compared to the other healers in terms of damage, especially when the other healers bring raid buffs to the table or some form of utility - WHM doesn't bring enough. Holy III also is for some ungodly reason a 2.5s GCD compared to AST's 1.5s Gravity.
Liturgy of WHM Harm - As much as I understand Liturgy is supposed to be a large heal or multi-heal akin to SGE's Panhaima ability, it's a horribly designed ability. Why? It requires you to get HIT. WHM has absolutely no agency after they hit this skill, making it too niche to use in most situations other than set and forget. A Capstone should give the player agency to be a good ability, not just a passive heal that requires the player taking detrimental damage.
These issues are among the most prominent of WHM, and needs be fixed.
We do have solutions, however:
Raise Afflatus Misery to 1240 potency. This makes Misery DPS neutral in all cases, and increases its potency to match with the likes of Glare III and ensures that you don't lose DPS because you use Lilies.
Add a detonation button to Liturgy of the Bell. This grants the player agency on WHEN to blow it up, similar to how Macrocosmos has. This means you can place it then detonate it immediately for a BIG HEAL.
Add 800 MP Recovery to Lily usage. This balances out WHM's MP Economy in long term fights, despite it requiring 30s to charge. If a WHM is handling their MP properly, they should not run out of MP.
Secondary Suggestion: Make Lilies oGCD. As much as some will say "Oh, but it's the same as SGE/SCH! We can't let them have that!", this will allow WHM's Misery to ALWAYS be a gain no matter what. This idea should be considered if Afflatus Misery potency buffs are not the way forward with design.
Lower the cooldown of the lilybell from 180 to 120 seconds. Doing this would allow Liturgy to feel more useful in terms of application, and not be limited to niche situations.
Other healers have some form of healing burst, while WHM surprisingly has a huge lack of it for being a Pure Healer. Assize is literally just that burst, but it's also DPS, so giving a second charge to Assize might help it.
If there are any other ideas, I'd like to hear them in this thread - they will be added to the OP provided they are substantiated and the community agrees.