As others have said, healer DPS is by far the most important part of healer in endgame content, as they do a non-negligible amount of damage and thus clearing content requires healers to maximize their damage output. The healing is actually secondary, all healing choices made are made to avoid using GCDs on healing (Medica, Medica III, etc.) and instead maximize GCDs allocated to DPS abilities (mashing Glare). This means that if you somehow end up with a less competent co-healer, or your tanks are not using mitigation, or your DPS are not using Addle/Feint/Magick Barrier/Tactician etc., then you inevitably have to sacrifice your own contribution in order to make up for your party's shortcomings. But on the flipside, if all goes well and everyone is using their stuff properly, you push 1 oGCD (i.e. Liturgy of the Bell, Macrocosmos, Panhaima, Seraph, etc.) to resolve the hardest mechanic in the fight and continue to spam 1 spell over and over and over again. So it's like a "damned if you do, damned if you don't" situation with healing: if you heal well or your party mitigates well you are rewarded with more Glares, which is boring, but if you don't heal well or your party can't use mitigation well, then you're punished with lower DPS and possibly hitting enrage. Neither feels good.
I think they need to bring back Stormblood job design to some extent for healers if they intend for healers to be played like some kind of green DPS with healing attached to it (because that's really what's going on here). Have slightly more complex DPS rotations to make the combat feel more engaging and be more rewarding for when healing/mit is done properly rather than being graced with more single-button GCD usage. Tanks IMO have had it a fair bit better, like a gunbreaker who knows the fight well can greed for full uptime and keep their combo rolling which feels pretty good in practice. Healers need something like that.