People are discussing the Stormblood abilities and all other kind of problems, but if you want to discuss WHM, you should start at the beginning, i.e. the base toolkit of WHM.

You have the three Cure Spells: Cure, Cure II and Cure III (AoE).
You have the two Medica Spells: Medica (AoE) and Medica II (AoE HoT).
You have a HoT Spell: Regen.

Which of these spells are redundant?

Cure III: Medica and Medica II provide more than enough AoE healing, if necessary Assize and Assylum complement it.
Cure I/II: Regen is far more efficient than Cure I, Medica II is up for a fairly high amount of time, if AoE is going out, you priorize Medica, if you need big single-target heals, Benediction and Tetragrammaton take priority.

Now come the Stormblood Abilities: Lilies and Confession, that are majorly based around Cure I and Cure II, probably to make WHM actually use their Iconic spells.
Just that Medica, Medica II and Regen still vastly outperform all the Cure Spells - and suddenly you have a giant mess of abilities in Stormblood.

The simplest way to fix it would be the radical one: Remove Medica and Medica II.
Then, continue with something like:
- Regen is limited to one target, but can proc Lilies
- Cure III can also proc Lilies.
- Lilies proc far more conistent due to regen/casting cures.
- AoE Heal will be handled by Cure III, Assize, Asylum and Confession. (this is still 4 AoE healing abilities, with Lilies actually being more readily available)
- maybe Add some sort of group damage support based around Lilies Consumption (trade healing vs. group damage)

AST then could become a HoT Healer (i.e. Remove Shields from AST), while WHM focues on big direct heal to get the group up.