The unfortunate fact is that it's been visibly demonstrated time and time again that at least as far as healers go, SE only really seem to pay attention to clear rates of various levels of content.
I've stated this before but incase it's been missed:
AST was absolutely nowhere in Gordias and rightfully got extensively buffed and adjusted to make it competitive. Any proper QA should have highlighted that it was just not equipped to deal with Gordias Savage.
It was handily the equal of WHM for Midas but Noct wasn't competitive with SCH. SE didn't seem to understand this, merely seeing that it's usage was still down resulting in a completely misguided series of buffs that saw it relegate WHM to the bench for Creator.
Meanwhile concerns had been raised over WHM's long term competitiveness vs SCH and AST throughout Heavensward. These were completely ignored. When patch 3.4 came along and AST made WHM functionally obsolete in Savage WHM still saw good usage in more casual content and thus nothing was changed despite all the complaining here and elsewhere. Patch 3.5 rolled out and people literally started excluding WHMs from PFs for extremes and sometimes even lower tier content. SE finally reacted by plugging some of WHM's issues with the SB kit.
Deltascape saw SCH have it's first turn on the bench, it promptly got a wide range of buffs, fixes and abilities. Again, any experienced healers on the QA team should have highlighted that this iteration of SCH was going to be dead on arrival (and should have flagged up AST's hefty QoL regression as well).
I wonder if a part of Yoshida's reasoning that healer's are currently 'fine' is that these days, healer clear rates are all fairly well balanced now. I don't think they are invested enough in the healer role to actually sit down and look first hand at how dire the gameplay is especially in casual content. Rather they are just getting random test teams from SE's pool, potentially with little experience of the game and going with them for feedback.
There's no denying that in the eyes of a sprout, healing in this game is exhilarating before you've started down that haunted optimisation path.