Apparently, it would be "too confusing" having different polymorpher skills based on different attributes, and people would dislike having to invest into different attributes for different skills in the same school.
It's a bit disappointing, but I can understand the logic.
Has Larian made a statement somewhere on the polymorpher skill tree? I'd love to read it if so. It would be a little more confusing, but, it really makes sense to have a monstrous creatures stats effected by base strength/constitution/finesse of the character its morphing from, right? I'm actually not a big fan of warriors, I much rather other classes, but I really feel for the class.
I think to some degree it would be a missed opportunity if you couldn't have a warrior turn into a hulking beastie and be effective with it