There are several ways we could approach modifying the healer kits. I was putting together some quick solutions that could be passed along for a survey. The goal I was going at was working with the current systems we have and adding to them. Our toolbars are getting full, so we need to be mindful of that too. Merging 2 buttons doing similar things is a method to free up a button slot. The thought of lilies having a DPS option did occur to me on some thoughts that always feels like the best option since killing the enemy faster with more DPS has most often been the best utility. At that point, we may have to have a vote if the players are alright sitting on Lilies / Addersgall or if they wish to have a way to use them differently when no healing is needed. Another avenue to explore is that all the healers are ranged at this point. If we look to Warcraft, we have a few potential melee healers there with Paladin, Druid and Monk. Having a combo system for one healer could be interesting and the healer tends to need to hover close to that melee range anyway so their 30 yard centered AoE heals get everyone.
As for the AST class you didn't comment much on, I usually see players complain they want the old cards back. We kind of don't have TP anymore though, so "The Spire" would need something new like a movement speed boost if we go down that avenue. Maybe even some way to allow casting while moving too. At the very least, I would like to see Royal Road come back to some capacity, so we can get those AoE card buffs or maybe an extended version on our selfish DPS bursting the hell out of an enemy.
An additional thing I would like on SCH would be a fix on Dissipation. For the most part, it just feels like an extra Aetherflow cooldown with restrictions on a 3 minute cooldown. That one players suggested that the increase in healing magic potency to be extended to all oGCD ones too rather than just Adloquium and Succor only ... well Physick too, but that one rarely gets used being the "cure" spell for SCH. Why on Etheirys does it not buff oGCDs when it grants you 3 Aether for oGCD heals? Also having the fairy still being there with us will help a lot too.
The AoE Kardia effect from Soteria and Rhizomata granting both 1 Addersgall and Addersting I agree with. I do use the latter cooldown since Taurochole and Kerachole are important for damage reduction on the tank. The DPS sometimes need that Druochole for mistakes that have occurred after all. The first Soteria cooldown does not feel very impactful though and it would have been a much better choice to use Haima or Panhaima on the tank.
WHM I think does have a robust kit that is simple with its effectiveness. Being able to spam stun enemies is really strong and works very well paired with Regen, Medica 2 and / or Asylum. Most cases, I notice the players wanting to be able to use the Stone, Water and Air elements. We kind of drifted away from that with having Dia and Glare creating a light only damage healer.