Let me tell you a story of how a healer was once (re-)designed in a certain MMO. It was a melee class with it's damaging abilities intimately tied to it's healing output despite only having 3 DPS buttons and a couple of basic healing spells.
First, it had a long-lasting but weak regen spell that would automatically hop to a wounded party member if it's current target was at full health. The spell had a cooldown, so you could only ever have a limited number of players regenning at a time, but it was nice. Weak, but a nice side bonus - kind of like fairy passive healing. The real key was the regen buff's interplay with other abilities.
The DPS kit was based around three melee "spells": a punch, a roundhouse kick, and... let's call it a drop-kick. The punch did light damage and added a stacking buff, with a cap of 3 copies, that did nothing inherently. The roundhouse kick did decent damage and consumed the aforementioned punch buff to copy itself while restoring mana for each hit landed. The drop-kick was mana-expensive and had a cooldown, but also burst-healed every single player with your regen buff on them.
There was one other, crucial, sublime element: taking a drink. The class had an ability - oGCD, in XIV terms - to take a drink that would buff the next major ability you used. It's important to note that the cooldown (~30 seconds IIRC) was less than the length of the class' regen buff (~45 seconds IIRC). Now, if used before your regen, you could place more copies on more players. If used before your drop-kick, it copied the drop-kick (including the heal).
The play pattern should now be obvious. There were other spells and abilities, including other possible drink buffs, but the core pattern of this build was to deal as much damage as possible while passively maintaining mana and putting out sustained healing. If a damage spike was approaching, you would drink up and buff your regen ~30 seconds in advance and then drink to buff your drop-kick as the damage spike landed. If you didn't drink to the right abilities, or messed up your DPS rotation too poorly, you would use too many inefficient strikes and wind up ineffective - either by putting out too little healing or burning your mana too quickly. It required more forethought than any healer in XIV.
Sadly, it turned out that there was only one bossfight where this build was mathematically strong, at least for my guild. The right and proper way to build and play the class was much less engaging. If this dps-focused healing build had been tuned to be stronger, and therefore something I got to play regularly... well, I probably wouldn't be here. I'd still be fistweaving. Unfortunately, I have learned that XIV healers are even shallower than the boring mistweaver builds that I fled. I'll probably continue playing for a bit, using Bard and/or Black Mage, but I expect to be gone before the next expansion. I am, after all, in no way interested in slamming a single button for the vast majority of my game time.