It's funny how much the overfocus on balance in numbers in raids has reduced healer design space in particular. Back in older MMORPGs you had a single game that had these four healers:
* A pure healer, with a cleric stance like thing they had to go into or out of to even be able to deal any damage at all really.
* A buffer, who could actually heal a fair bit but... indirectly. Like you could give someone very short buffs to their absorption or so, like external 40% DRs. In return, weaker heals and damage was also indirect via buffing people. Since all your buffs were casted + short, you were quite busy.
* One healer that gave their own health away via a mix of heals and HoTs, and then constantly had DoTs on enemies to drain health back to fuel this. High overall output, but fragile if there's ever a gap.
* Lastly a healer that designated a target and then went melee, causing healing around them and on that target.
Were these balanced? Not in the slightest. Were they fun? Hell yeah!