Physick (from ACN4) isn't a real thing, at least not in parties. Solo, it finds occasional use if you need to Sleep something and then spam Physick on yourself.

In a party, if you're in a situation where someone needs healing so badly, Physick will not restore enough HP to make a difference -- that is, if it seems the party was "saved" by BLM Physick, the party still would have survived if the BLM had been casting splody spells instead (and this is really the preferred method of survival for those who would rain destruction from the heavens). Cross-class Physick only serves to prolong a fight with no positive change to the outcome.