How to go about More Involved DPS Rotations.

[GrimGale]

Well that can also be adjusted. Maybe applying debuffs could give extra FG, or maybe crits from your adlo and physick could also increase fairy gauge. Or everytime Fairy uses embrace she gains fg too.

[Archwizard]

With regards to creating more complexity with Healer DPS rotations, this big thing isn't necessarily in "how" to do it, but rather in how "much" to do it. Bear in mind that regardless of the number of buttons you're hitting, you will ideally do less damage than any DPS on the team (not simply for balance reasons, but so the overall rDPS loss when you stop to heal isn't bigger than letting your lowest DPS die).
Set up too high of a skill hurdle for too little of a reward, and you end up with extremely busy yet low-performing jobs like Ninja.

So, I would like to propose thus:

1) Tie some elements of the healing side of the kit into their core DPS rotation.
There are multiple ways to go about this.
The most direct route would be to follow the example of White Mage's Holy skill, which inflicts a brief but potent detriment on enemies it affects, drastically increasing the tank's survival for a brief period through the healer's direct intervention. You could give similar tools to SCH and AST's respective AoEs, like a Slow on Gravity or... something for Art of War. Or to be less derivative, have Broil inflict damage down (by aiming at the target's weaponry), Glare inflict Blind, or Combust curse the target somehow.
Alternately, as OP notes, another aspect of this could be having DPS abilities for resource management. Cast Stone/Glare to speed up Lilies, cast Malefic to regain MP, cast Broil to speed up CDs or drum up procs, etc.
All of the above provide tools where even though you're not directly healing, it doesn't mean you're not contributing to healing or survivability in some way, so nobody is allowed to complain you shot the boss instead of throwing them a Cure. (They'll do it anyway, but this way you can say "I needed MP" or "I just saved your life and got more out of that than a Cure but go off".)

2) Create high-risk, high-reward DPS tools for each healer.
I don't just mean "high risk" in the same way getting greedy with a Stone/Glare means more hits on the tank. I mean have potent DPS tools that actively compete with the healing tools you have within the kit.
For instance, having a damage skill that consumes Lilies as a White Mage -- you're consuming resources that are used for potent and expensive healing in order to dole out more damage. You could do the same thing for SCH or AST by having damage skills that share CDs with their healing oGCDs, creating scarcity to encourage the use of their GCD heals.
Alternatively, giving a "Cosmic Alignment" buff to AST or "Press the Advantage" to SCH that increases their damage slightly but cripples their healing until it ends, like the old old old Cleric Stance.
Why? Because this way you can set your own skill ceiling by choosing how cautiously you want to play.

3) Give back the ability to spread DoTs in AoE.
Fairly self explanatory. Our AoE rotations consist either of spamming one attack and maybe a CD, or manually multidotting. The former is even more boring and the latter is painful, especially in the case where you have to heal the tank between casts.
You could even give healers abilities that have the Thunder 2/4 treatment, where they're mutually exclusive with other DoTs. Point is, let them spread so we have more to do and less time wasted doing it.

Now, that being said, I have some different ideas than OP as to the "how" for existing healers.

WHM: The last thing our lovely mage needs is more MP recovery. At present between Lily heals, Thin Air and oGCD heals, it's so good at eliminating costs that I can press LD maybe once per fight if I'm playing badly.
That said, I'm not entirely sure what WHM could use. A Lily spender to attack with? Another oGCD attack?

SCH: To the contrary, I actually think we're ignoring that SCH once WAS the DoT-focused attacker amongst our healers, until all Miasma effects, Shadowflare and Bane were removed from its kit. Most were fire-and-forget, but you still had to manage with an extra DoT and without SMN's Tri-Disaster.
I would almost be willing to suggest a proc of some sort as well for Ruin II, though that would just piggyback off of Ruin IV for SMN.
I could also suggest throwing some counter-attack effects on the tank -- sort of like Eye for an Eye, but more literal Spikes effects or even straight-up Reflect, use tactically and time the cast perfectly to slap a boss in the face with its own tankbuster.

AST: Meanwhile, this is the perfect repository for self-buffing skills. Alternately, for damage buffs in general; I have half a mind to say AST's damage contribution should largely come from the time spent applying buffs to higher DPS individuals. Of course that would be no less boring, exhausting, and unhelpful for solo content.
Funnily enough, AST is also the healer I would say is most in need of MP management skills, especially with the losses of Ewer and Lady of Crowns.

Personally with regards to a fourth healer... I admit I'm biased since I have tried to push Necromancer as a battle healer, but at the same time, I think having the devs work on a job whose kit is "deal damage in order to heal" might give them some needed perspective on the damage tools available to other healers, much as working on Gunbreaker gave them perspective on how to balance existing tanks.

[Lola_bunny]

I like the idea of making the dps a bit more intelligent but my only concern would be for the small percent of actually intensive healing fights. Just talking about my limited experience in high end content with AST (and I realize give how clunky the card system works now not the best example) but when dodging mechanics, making sure no one is dying, trying to keep combust up and active, checking the tank, it's easy to forget about managing my cards. So I would be concerned either having a dps rotation or more involving dps abilities in general will be another thing to think about and keep tabs on during fights.

I'm torn on it on the whole, it would give the classes a higher skill ceiling but that would also bring elitism in spades to the high end content where there's already more than enough there. You can't perfectly optimize get kicked. A tad hyperbolic and worrying about what if scenarios to be fair. I'm also being a bit honest about my own abilities, I want to do and learn the end game content so I'd be hesitant about adding complexity as It'd make it more difficult for me to learn the fights and keep optimized. My hesitation around upping the thinking involved when healing aside they all need a bit something. They need to be more than just okay.

[Billythepancake]

I like the idea of making the dps a bit more intelligent but my only concern would be for the small percent of actually intensive healing fights. Just talking about my limited experience in high end content with AST (and I realize give how clunky the card system works now not the best example) but when dodging mechanics, making sure no one is dying, trying to keep combust up and active, checking the tank, it's easy to forget about managing my cards. So I would be concerned either having a dps rotation or more involving dps abilities in general will be another thing to think about and keep tabs on during fights.

I'm torn on it on the whole, it would give the classes a higher skill ceiling but that would also bring elitism in spades to the high end content where there's already more than enough there. You can't perfectly optimize get kicked. A tad hyperbolic and worrying about what if scenarios to be fair. I'm also being a bit honest about my own abilities, I want to do and learn the end game content so I'd be hesitant about adding complexity as It'd make it more difficult for me to learn the fights and keep optimized. My hesitation around upping the thinking involved when healing aside they all need a bit something. They need to be more than just okay.

I've raided on Stormblood with SCH, whose DPS kit was quite a bit more involved than we have now, and honestly, it's not that bad to keep up with. While you're learning the fight, sure you'll drop something here or there because you have so much new information flying at you, by that goes for every class. Besides,imo, that's the fun part. Learning to juggle all your dots and everything else on top of doing mechanics and keeping people alive.

[YusiKha]

Slow on Gravity or... something for Art of War.

A blind for AoW?

WHM

My plan was for Stone/Glare to become more expensive (600-800mp per cast) so that WHM would have more mana issues just going through its nukespam. This would facilitate the need for an on-demand ‘gimme mp!’ button that would also allow you to weave at will (an issue WHM still faces). The addition of essentially Darkside would further push WHM through MP economics questions. Afflatus and Regen’s MP superiority would be much more impactful by reducing the amount of water/osmose casts, even if Cure2/Medica fed the Blood Lily.
WHM would have a safety pick argument in their infinite MP and efficient healing GCD usage. Compared to SCH’s mitigation+shielding, and AST’s larger shields.

SCH

My reasoning was that despite SCH’s past, many/strong DoTs would be better for a GCD focused healer because of their weaker nuke. DoTs could work for SCH, though, if they were the only way to weave without clipping a cast.
Reflecting things like tank busters wouldn’t work as SCH’s damage would differ depending on the encounter. I would like to see Aetherflow moves to a mitigation/damage resource and more emphasis put on the fairy for actually healing.
A way that the counter could work is an AF skill you place on someone with Galvanise. If galvanise breaks before the duration is up, the attacker gets hurt. If catalyse also breaks, the damage increases. (Maybe be able to deploy it too?)

AST

Yeah AST needs something for its mana. Though for the rest of its kit everybody has their own ideas, massively varying. I do want Comet, though.

[GrimGale]

Well AST is the healer that doesn't need more involved dps mechanics. I'd go full cards with AST if I were to redesign it. I'd shorten Draw CD as to allow the AST to constantly fling cards at party members and improve on the rng and buff manipulation, so that they'd be kept busy with buffs management and healing.

That way AST would truly feel unique.

[Dzian]

Think of it as the DPS “rotation” as more engaging instead of complex..

The problem though is rotations generally aren't engaging anyway. Just the same skills in the same order time and time and time again.

Pressing 12 3 1 2 3 1 2 4 12 3 123. Is really no more engaging than 1 1 1 1 1 1 1 1.

Doesnt matter what fight your in or which boss your up against it's still the same rotation as every other fight or boss...

Rotations aren't fun or engaging especially when so many of the skills and buttons jobs have to press are literally just "busy work"

[YusiKha]

The problem though is rotations generally aren't engaging anyway. Just the same skills in the same order time and time and time again.

Pressing 12 3 1 2 3 1 2 4 12 3 123. Is really no more engaging than 1 1 1 1 1 1 1 1.

Doesnt matter what fight your in or which boss your up against it's still the same rotation as every other fight or boss...

Rotations aren't fun or engaging especially when so many of the skills and buttons jobs have to press are literally just "busy work"

“Main Class Paladin 80” yeah that makes sense.
I’d rather busywork than the ability to play The Sims between 2.5s broil casts

[Billythepancake]

The problem though is rotations generally aren't engaging anyway. Just the same skills in the same order time and time and time again.

Pressing 12 3 1 2 3 1 2 4 12 3 123. Is really no more engaging than 1 1 1 1 1 1 1 1.

Doesnt matter what fight your in or which boss your up against it's still the same rotation as every other fight or boss...

Rotations aren't fun or engaging especially when so many of the skills and buttons jobs have to press are literally just "busy work"

The more you have to manage the more likely you are too drop something, making it more rewarding when you don't drop anything and giving off a better feeling of satisfaction. I'd rather have busy work than just spaming 1 over and over again. I don't need much, 3 dots and something like shadowflare (maybe not a ground target though) and I'd be fine with SCH dps wise.

[Dzian]

I'd rather have a few buttonss that actually do something. Rather than buttons just there to keep you busy but dont actually change the fight