Physick is a legacy of the cross-class system and had nothing to with end-game SMN or even being needed for SCH - it was because ACN was a class that locked new players to starting in Limsa Lominsa, and because Limsa has no access to the rest of Eorzea until you complete the level 15 main scenario which unlocks airship travel (and the Limsa-Vesper Bay ferry), they needed some way of allowing new players who started as MRD to be able to cross class a healing spell. Players who started in Ul'dah didn't have this issue as they could just travel on foot to Gridania and unlock CNJ for Cure, Limsa players did not have this luxury.

Thus, ACN was the only way they could add a healing spell as a cross class spell early on for Limsa players (unless you counted the original version of Bloodbath a 'healing' ability). Of course, the cross class system is gone now, but some legacies of it still remain, Physick on SMN being one of them, it's meant to be an early cure spell that helps you out at the start of the game but by end game it's useless (if equipped with SMN).

I would prefer it if SE added some kind of pet-given buff that increases healing potency irrespective if you're SMN or SCH but other than that, it really is pretty useless as it is now sadly. So I can definitely understand the calls to remove it.