The main issue with this happening is that it's more optimal and not even more dangerous despite not having a healer, as long as everyone follows the mitigation spreadsheet to the letter.

No healer runs have been happening since ARR, this is true. But no healer runs back then were actual challenge runs, it wasn't easy and it was much slower than a regular comp run.

But after EW (and ShB, to a lesser extent), it became optimal to just drop the healer entirely, because it ends up being not anymore dangerous than normal and it's also a faster clear.

Healers right now are the worst in damage output, so if the extra healing power gained from bringing one isn't even needed, then healers are just worthless. One entire role being completely worthless as anything except safety insurance is extremely bad trinity design.