An arguement towards having Healing on DPS

[Archwizard]

Edit for clarity: Emergency means emergency. Vercure is an exception in that it is an emergency utility that is available on-demand on the GCD.

Barrier skills on DPS fall under the "emergency" category and don't affect enmity generation. Apples and oranges. No slippery slope in danger of being navigated.

Yes, I've seen plenty of bad RDMs since their release.

It's not apples and oranges at all -- your argument was that players would use the tools outside of their role to attempt to do the job of other roles (as Vercure/raise allows RDM to dip into group healing).
At their most efficient use, barrier skills are often utilized by DPS to soak damage-heavy mechanics, and in extreme cases they have been popped to give a high-aggro DPS some time to hold the boss until a tank is revived. Hell, two of those mDPS have stances that give them low but indefinite mitigation at a damage loss, while SMN's use of Titan-Egi has always been affiliated with some minor form of tanking. Those are cases where DPS explicitly hybridize into tanking roles.
And as I also stated, effects like Apocatastasis and Erase allowed all caster DPS including BLMs to perform a healing role in a minor capacity -- Erase itself was even a priority over Esuna in some cases, given that it was free and oGCD.
So it's very curious to me that your position is specifically in naming every other edge case an "exception" specifically to disallow SMN from having a viable Physick effect, or BLM from a spammable self-healing effect.

Furthermore, the question wasn't "How many bad RDMs have you actually seen," it was "How many bad RDMs have you actually seen ignore their responsibilities as a DPS for extended periods in order to do the incumbent healer's job?"
One or two? Five to ten? Dozens? Hundreds?
Because your argument hinges on a grand number of new players specifically using their late, singular healing ability to attempt to perform an entire other role from a DPS position at a meaningful level, and I find it hard to believe you've seen such an extreme number of confused new players as to justify not giving any more non-emergency healing skills to other jobs -- or in this case with Physick, to justify not buffing an existing skill which, if you were right, would already be subject to exactly the same confusion even after Sastasha.

It reads to me like you saw it happen a couple times and generalized it, instead of just telling them to DPS and let the healers do their job.