I really don’t think it’s a good idea to try and make every healer functionally able to fill every niche; whether it be by actual skills that can fill every niche (like modern SCH) or a toggle that swaps actions to fill different niches (like nocturnal and diurnal sect), the healers should have defined niches that work better in some situations and work less well in other situations (I’ve always said the armoury system should encourage this sort of thing, if fight 7 favours SCH and fight 8 favours SGE you should swap for the two fights, not just make every fight clearable on every comp), the problem comes from the all or nothing encounter design (whether that be modern design that favours mitigation or older white hole design that favours pure healing)

I really don’t think the regen/shield split is inherently a bad thing; if anything giving particular niches to healers is a good thing, but they need to find a better way to make sure single healer content isn’t messing up group content

I could propose 2 things here
1) skills have different effects in solo healing content, for example succor only has a pure healing aspect in single healer content or indom can only crit with recitation in single healer content
2) make it so in DF duties with 2 healers you always get a regen and a shield healer (except maybe if you queue together and are willing to risk it), this avoids the “well how can we do white hole mechanics as double SCH without succor healing, critdom or ET

Then in group content they need to reduce the over reliance on pass fail mitigation checks and up chip damage, this gives both healers a niche, discourages SGE/SCH and makes it feel like both healers are genuinely contributing as an individual player rather than just contributing as one of the two faceless healers