As long as no one bullies me in raid for not using it and prefering my primary role, you can base Physick on whatever stat you deem relevant.

"Meh, should have physick the tank after that TB" - Not my job (and yes it's different than healers heal/DPS strawman, cause it means not only lost GCDs but also lost focus on a rotation more complex to keep up than healers' DPS)

I personally think you shouldn't though, and Vercure, to me, is a mistake the way it is (not in solo where it's nice, but out of place in a raid environment with a role trinity)