A video was recommended on my feed recently of Dancing Plague Normal where the run was supposedly carried by healer.
What actually happened was the player (WHM) keeping a full up-time of Medica II. Meaning, they constantly reapply Medica II the very second it falls off. It was really hard to watch (I clicked off at 50s).
The Aggro thread makes me wish overhealing would still rip aggro from tanks. Though I am unsure if it's possible to code to make it work. It doesn't add much engagement to healer's gameplay but at least it's something the average DF healers have to be wary of.