Idea for AST healing
This is all with the thinking that SE would actually change the DOT tick to be every 1s instead of 3s. If it's still 3s, change the duration values below accordingly (also they're just spitball and not actually balanced)
Most oGCDs have, ideally, a newly implemented system that shows they have two charges, but only one is useable (we'll get to that in a sec). These OGCDs would be Horoscope, Star, Exaltation, CI, CO, CU (god damn it SE please stop putting 'celestial' in front of everything). Additionally, Aspected Helios and Aspected Benefic are changed to have 'new effects, we'll get to below.
Both Diurnal Sect and Nocturnal Sect are back as buttons to press and swap between mid combat, and is the core of the gameplay for the class. Neutral allows you to be in both at once.
In Diurnal, the above OGCDs and GCDs will apply a Regen as they do now. If they don't already (Horoscope, Star), they now do their potency as a short duration Regen instead. Additionally, Horoscope is no longer a 'power it up with a GCD', instead acting as a regen who's ticks get stronger the further into the duration it goes, with the final tick being the strongest. (Maybe like, 100, 200, 400 and falls off). You can only use the 'Diurnal version' of the OGCDs in Diurnal Sect, but they do not share a CD with their Nocturnal version counterpart.
In Nocturnal, no skills apply shields, nor % mitigation. Instead, they each apply duration to a buff that I do not have a name for, so I'll just refer to it as Retrograde because that's apparently where a planet looks like it's going backwards. This Retrograde would stagger the damage taken during it out to be a DOT of equal damage per tick, based on the remaining duration. You can stack up to X seconds of this Retrograde buff, as decided by devs for balance, I'd say 30s. the GCD 'shield heals' we have would exist as a 'oh bother I need to use this but I've spent all my OGCDs like a silly billy' panic button. Asp. Benefic should give 15s, Asp. Helios should give 5s. Any overhealing caused will instead heal off extra 'damage compiled' in this DOT. Note that certain things do not count as 'damage' and will not be compiled, eg 'HP is set to 1' mechanics. Additionally, DOT effects are not compiled, and will tick in addition to the compiled Retrograde DOT. For useability, Retrograde would not start ticking until the player with it receives an instance of non-DOT, non-ground effect damage.
As an example, lets take a raid boss. Aionagonia, everybody's favorite. It hits the party for a theoretical 40k, plus leaving a bleed on them that ticks for 5k every tick (remember, DOT ticks are 1s in this hypothetical). Hypothetical numbers. We go Nocturnal, place down CO (+5s), CU (+5s) and detonate a Star (+10s (it was charged)) so we have 20s of Retrograde. Aion hits us, and we take 40k, plus get the 5k DOT for 12 seconds (I think it's 12 it's been a while). 40k divided by 20s is 2k per tick, plus the 5k from the bleed, so the party is taking 7k per second. We swap to Diurnal and put up some regens to counter this (remember, the regens are also 1/3 as strong per tick now, because the HOT tick is 3x as often).
Then lets say, we're actually doing Dominion. So at 8s left of the Retrograde, we are hit by the Dominion spikes for 64k each. Now that remaining 10s recalculates, it's got 16k left to deal out from Aionagonia, plus a new 64k has just been added into it. So we've got 80k over 8 seconds, or now spiking to 10k per tick from Retrograde. So we need to apply MORE regens now, because the old ones will be falling off halfway through this burst of extra incoming damage, and people will need to be spread to take their towers. Alternatively, instead of adding more regens, we could also add more Retrograde duration, by going back to Nocturnal and using another skill there, such as an Asp. Helios (+5s). Now the incoming damage recalculates again, 80k over 13s, and changes down to a more manageable 6,153.8 per second.
The key here would be the understanding of how much Retrograde 'staggering' you need to make the damage manageable, versus how much Regen effect you need to counter that. Overspending on an earlier raidwide might leave you high and dry for the next one, forcing you back into using GCD healing to make up for the mistake. Also, remember that you're a Pure Healer as AST. This means that your Cohealer is a Barrier (usually) and this means that they can mitigate the initial hits from raidwides, which lowers how much gets through to Retrograde, which in turn lowers the damage per tick even further.
This would probably be horrid to try and actually play, especially if it's on AST with the cards to manage too. Though, changing Lady to be a 'delays damage into a DOT' effect might make it a little more interesting than it's current 'maybe you don't have to cast a Helios' form. Ideally I'd make this an entirely seperate healer but we just got SGE and they can't balance what we have so, y'know. I was also considering having Retrograde store up positive HP change too, so you could essentially 'buffer Regens' so that when a raidwide hits, it'd automatically start ticking back up, or ticking up and down at the same time as the HOT and DOT fight, but that might lead to some degen stuff where you place the Regens on people with GCD heals in downtime, then use the OGCDs during uptime and get way more use out of them than intended