This is not a thread about whether or not more advanced rotations are what healers need, but how they could be implemented.

So, let’s pretend that we all agree that the best way forwards is for healers to get more complex DPS rotations. Slightly easier than tanks, and affecting their healing or other class subsystems.
Which ways could this be achieved? My thoughts are as follows:

WHM - MP Management
WHM at current is the God of mana efficiency with Thin Air and Assize, as well as the Afflatus Spells and Regen.
This could be expanded upon by making Stone/Glare cost more, but giving them a Water/Osmose Spell that, while weaker, restores MP.
To tie it into healing, maybe Cure2 and Medica1 could also feed the blood lily, but their inherent MP cost would make them further damage sacrifices than the corresponding Afflatus skill.
It could be expanded upon by giving WHM a stance that drained MP but guaranteed Direct Hits. This would also make PIE and SPS more interesting for WHM.

SCH - Self-Buffs & Resources
SCH used to be the king of DoTs, but their healing identity is all about oGCD Skills, which doesn’t really mesh well with an emphasis of ongoing damage. So instead we look at Aetherflow and Strategems.
Scholar could use more ties to the strategising lore identity it has, so I’m thinking more Aetherflow skills that don’t heal, but instead reduce incoming damage while buffing Scholar’s own (makes for more interesting dumps than energy drain). Eye for an Eye as well as Virus are old skills that could make a return as Aetherflows, and Soil could restore a portion of damage taken instead of being flat regen. These skills would give Scholar a ‘Strategem’ buff that increases damage (maybe crit rate for healing too?)
I dunno. Scholar is in a really weird place right now, and doesn’t really tie into its old lore or previous incarnations.

AST - Proc & Weaving Management
AST is currently the movement and weaving king thanks to its 1.5s cast time on Malefic, and needs an involved rotation less than the other healers due to the busywork in managing cards. AST will be the lightest change of the bunch.
2.5s Malefic returns, but so does insta-cast Stella. Combust ticks would have a 50% chance to upgrade Stella into Comet (stacking like ruin4), which deals the same/more than Malefic.
This could be expanded by having held cards giving Malefic an extra effect (maybe MP for Lunar seals, damage for Solar seals, mitigation for Celestial seals?) under the guise of Geomancy spells.

NEXT - DoT Management
We need a 4th healer, and we have 1 GCD focused healer, and 2 oGCD focused healers. DoTs work with GCD healing, and could facilitate a plague doctor, chemist, or biologist type aesthetic.
Multiple DoTs with varying lengths, Thundercloud procs to keep timings variable? Healing GCDs used could contribute to the length or strength of a DoT as a return on the lost damage Spell.

I welcome any feedback people have about these suggestions.