First of all, that's a scenario that could be applied to any job. Tank isn't using their mitigation? Sure, we can "get on their case" so that the tank remembers to rotate/use their CDs. Tank forgets to turn the boss so the party isn't cleaved- similar story when half of them drop to the floor. What if the DPS isn't using any AOE skills in a W2W - similar story.
We don't take the approach of saying "take out all the DPS skills for tanks except one AOE and a single target, give them plenty of mitigation, self heals and mob controls so they don't get stressed over exceling at their rotation"
As I said previously and have seen for myself, in "normal" content a healer can literally do no - zero- DPS and no one will say anything- first of all because the content is still completed, and secondly because people likely are aware that the TOS constrains how this type of request can be made. So they don't say anything. So one button, two button, a proc, a combo- that wouldn't change unless it is in the content where it matters- and those healers already hit their DPS buttons and heal.