Is there some content where the queues don't require a party in the ratio of 1:1:2 tank:healer:dps? I'm referring to those. The number of jobs should be in that proportion, too, imo.
As for it being easier... I honestly think they're just not thinking hard enough. About this, anyway. I'm sure they're thinking hard about some things but they haven't prioritised thinking hard about varied and interesting healers.
I'd love a true pet based healer, with a short range, that relied on managing the pets locations for range.
I'd love a damage transfer healer, that had self-HoTs and shields, and could transfer damage from other party members to themselves (you'd have to be careful with this one, though, to make the risk reward playstyle worth it without it being OP). For that one I'd also give them the ability to transfer damage from themselves to enemies (neither of these damage transfers being 1:1 hp to hp, ofc. A healer could never heal a tank like that), that way a) it's optimal to constantly keep yourself not quite topped off, an interesting dynamic, and b) it would integrate healing and damage, as healing yourself would be faster when dealing damage, which would in turn let you heal your party more.
I'd love a HoT based healer where the HoTs interacted with each other, making each other stronger, or maybe the application of the third turns the first into a shield over time, and the fourth turns the third into a small damage buff, etc. You could use a bane-like mechanic to build up a super DoT (perhaps with the appropriate combination of heal/shield/buff for the specific mechanic) on the tank by combining them in the correct way then deploying it to the rest of the team.
I'd love a healer with super-strong burst heals that also applied DoTs to their targets (not for the full amount, obviously), so that you'd have to be careful not to overheal to make the most of your heals, and make sure not to use those when there was big damage coming. (Obviously they'd need regular heals, too, but I picture these as being weaker).
I'm not sure any of those are great ideas. I'm spitballing off the top of my head, but at least they're interesting. I respect SE enough to think that if they actually dedicated themselves to making more varied healers they could manage it.