Some commonalities I am seeing here are a lily rework, water based spells, exclusive protect/shell, top DPS amongst healers (especially if still lacking utility), more utility, and the return of once exclusive skills that were put in the role category.
I have to agree with all of those. Based on that here is what I am thinking:
WHM currently does not have a on-the-run offensive gcd other than Aero, but it's a DoT. So mechanics that force heavy movement puts WHM in a bad place and having to choose the lesser of two evils. There is a vacancy for a water based spell that is instant with a 2.5 second recast that's basically Ruin 2 for WHM. Its potency needs to be lower than base Stone but higher than Ruin 2, and will give WHM back the Fluid Aura finisher on trash we had in 3.0, minus the knockback. I would put its potency around 120-130. I would like for this skill to replace Repose.
To add to WHM water spells, I wouldn't mind having another DoT to keep up, and for it to be WHM's highest potency per GCD. So a water spell that also inflicts Dropsy and heavy 40%. I'm gonna go big here: 150 base potency, Dropsy duration: 24 seconds potency 30.
Exclusive protect/shell. Only issue I have here is WHM is not really a DMG mitigator. This doesn't mean they shouldn't have any. SCH is not a HoT healer but still has access through whispering dawn and fey union. We have Divine Benison, and on a short enough CD to be weaved after every other Aero cast. Since most damage is focused on the tank, and the majority of unavoidable AoE is magical, I believe and AoE shell would be perfect for WHM and give them additional utility that isn't OP, which should allow them to ascend to the top of healer DPS charts.
The lily mechanic I would prefer for it to remain passive, but how we acquire lilies and what they affect would definitely change. The lilies simply buff the WHM similar to greased lightning for MNK. They make the WHM stronger, and they make the WHM faster. They could also possibly increase the range on their AoEs including Cure 3. I would go ahead and tie the consumption of these lilies to Assize. It is our bread and butter ability as we cannot pass up 400 potency with no % reduction based on number of mobs, 400 potency cure to all party members in range, and 10% MP restore. Potency and range for Assize would be 300/350/400 and 15/20/25 yalms respectively.
Last would be SoTL2. What I would do here is add the range buff to the lilies I spoke of above. Prior to 68 you just get the potency buffs. A tier ability should improve upon the previous. Not throw in another useless mechanic. Jeebus man what were they thinking here???