Healing is not hard

[Renathras]

So Ren...

The model seems to have all types of healers, from melee to buffer to throughput, dps, no dps, etc. WoW has options because it doesn't have a rigid combat and class system (to the level FFXIV does), which allows for a lot more variance. It also has more than 4 healer classes. Even in Vanilla, it had 5 (only 4 per faction) which became 5 outright in BC when BE Paladins and Draenei Shaman were allowed. Then it added yet more after that (Mists added Monk, Dragonflight added the dragonkin one).

But the important thing is that they were largely allowed to be distinct, even Disc and Holy Priest branching from the same class and sharing a number of abilities (before they were eventually more split up in Cataclysm) were, though granted Disc was a poor performer until...Wrath?

Experimental effects being added is fine, but note what it's NOT doing: FORCING those experimental effects on everyone. It's keeping the old base models in tact alongside the experimental changes. The players are given the option to incorporate them OR NOT.