RDM needs Vercure for dualcast priming, it would lose little utility if the potency were reduced. (An argument can be made it'd be better if it were, but that's neither here nor there.)
Physick has no use case justifying it. This is why SMN has ogcd healing and barrier powers and RDM does not. If they made Physick useful, say good bye to your 20% HP barrier.