I haven't fully thought this out but I may as well think as I type. Tanks in 14 have an interesting feature. That is, their mitigations and aggro abilities like provoke and shirk are off globals, whereas all their GCD's are dedicated to dealing damage and minor passive effects like weak barriers (brutal shell) or self heals (storm's path). So their OGCD's are what makes them tanks while their GCD's are just their damage rotations with some tank flavored passives. Why aren't healers designed like this? Imagine if every GCD healers had was part of an actual rotation and if every healing ability was OGCD. Including things like succor or medica.
Side note, how would it feel if there were OGCD's with cast times? They'd obviously need to be short but i think it would be interesting albeit probably clunky. And healers rotations could contribute to their healing resources. Imagine sage. Cast dosis, it can proc duodosis which gives you a healing buff, it can proc tridosis which gives a gall. Everyone just took damage and you want to heal it but you don't want to consume a gall. Cast prognosis which has a 1.5 second cast time and is OGCD. This would largely solve the issue of heals being damage negative while making the game's design a little more consistent.
I'm sure not every heal would work as an ogcd as things like helios would blend with celestial opposition plus abilities like assize exist. It could also mess with WHM's lilies since their entire point is to refund you for GCD heals... And things like eukrasia would need to be reworked... Yeah this wouldn't work perfectly on jobs as they are now and would need a lot of work but I think it could be interesting at least to think about. Anyway, what do you all think?