Asking for any role to do less DPS will never be something people would embrace willingly. Also, would that not go against what Healers want, healing? I often read that Healers don't want to DPS, its why they play healer. Then why advocate for making Healer DPS even more mandatory than it already is?
Instead of forcing a higher/different DPS discrepancy, it would be better if the game actually brings in unique Healer mechanics that cannot be resolved by other roles. Make overhealing do something (like fill a boss debuff bar, that bursts into a short stun, idk) or bring in burst heal checks that require dedicated healer healspells.
And no, I have no idea what else those mechanics could be. I am not a Game Designer, after all. That would be something to figure out for Square Enix.