part 1: I would tend to agree, if we were on about just SCH in a vacuum. But if we're talking about incentivizing playing Pure healers over running SCH/SGE as a comp (to preserve and enforce the split rather than give up on it), then we have to consider SCH and SGE together here too, and as you note, SGE is pretty cracked on what it can do. Even if we took the lowest hanging fruit of design, of a constant DOT effect for a fight (A11S fire floor as an example), it'd have to do more than 4k damage per tick for us to even care, because a SGE/SCH comp can rotate Soil/Kera with 100% uptime and the trait's regen would breeze through that. And yet, the thought of taking 4k damage per 3 seconds is enough for a fair few players in this game to keel over to, so it goes back to the needle-eye we have to thread of 'how much damage is enough to burden our kit, but not too much to cause players to quit cos 'too hard''
part 2: Another thing that comes to mind that I forgot to mention in the previous post is the nuance of what shielding skills do based on their tooltips. For example, while a skill that says 'applies a shield equal to a 500p heal' and one that says 'heals for 100p, and applies a shield for 500% of the healed amount' sound like they would apply an equal amount of shielding, the former doesn't get reduced by things like Infirmity. This would open the door to potential cheese issues, for example, the Heartless Archangel debuff in O8S prevented any healing from occurring. With that former skill, you could apply a shield regardless of the debuff, unless SE were to code the debuff in such a way that it constantly removes shields for it's duration (I know it does on cast), and IDK if they want the extra bother of having to check if that happens correctly each time it's used
part 3: I would also agree that 'niches' would be nice, but the game just isn't designed for that re: fight design. We don't have a way to have, eg, classic WOW's 'Holy Paladin is crazy good at tank healing, Resto Shaman is crazy good at AOE, Holy Priest flexes based on comp, Druid cries because Priest does everything better than it can and is only brought for the res'. Instead, I'd rather the 'niche' be in the gameplay, rather than their dynamic/'subrole' in the team. eg, instead of saying 'AST is the tank healer because it has Synastry to get both tanks at the same time for bleed-TBs', saying 'AST is the delayed heals playstyle healer'. Playstyles can always be functional (with balancing), but a whole assigned-by-devs subrole like 'the healer that is really good at healing the tank' can end up feeling left out if fight design doesn't accommodate. As a great example, take a 2healer team from Classic WOW, and drop them into FF. You either have HolyPal/HolyPriest, or HolyPriest/RestoSham, depending if you were Alli/Horde. Now, in any given FFXIV fight in recent days, it's entirely possible that the tanks just... heal themselves for the whole fight. So, as the dedicated 'I heal the tank real good' player, the HolyPala for example, you're just out of luck on getting to play your role, because the tank's doing it for you. Or maybe the fight is just very AOE heavy, and the boss hardly ever autoattacks. Instead, making the differentiation be 'I heal with HOTs' vs 'I build healing resources via melee strikes' vs 'I heal with sheer HPS throughput' vs 'I heal via dealing damage' is just more likely to be inclusive to all classes regardless of fight design, rather than running the risk of one being ostracized for not being suited to the fight
But maybe that's too much optimism that SE would actually create 4 distinct healing playstyles, instead of just WHM, WHM2, SCH and SCH-but-smoothbrain
'When Eukrasian Diagnosis or Eukrasian Prognosis break, they leave a buff on that player called Second Opinion for about 5 seconds. When Pepsis is used, it consumes Second Opinion to heal that player for the amount of HP the barrier protected for. Essentially, if you ever played a Character Action game like Viewtiful Joe, Wonderful 101, whatever, and used the Ukemi (jump button right as you land, instantly heal back the damage you took), it's that with a bit more leniency. And it gives Pepsis a much more interesting use case.'
Something like that? I'm not on the game at the moment, and I've not healed with an E.Prognosis in a while, but from memory the shield (in BIS) would be equal to about 9-10k health? So this wouldn't heal for a massive amount (my not-in-party, no food HP on SGE is 74.4k), and requires a GCD-casted Shield to use, but it'd be something more for us to have 'some activity', and it's healing related (for the 'healers should heal more' players) which is a bonus. Numbers could also be tuned as needed (eg MP cost, CD, % of shield converted to healing, etc). Effectively, I guess we could consider it a 'Continuation' from GNB, but instead of our own skill, we 'Continuation' the enemy's skill?