I want to gear up my Freezing Arrow amazon and have a question regarding the stacking of piercing attacks from different sources:
if i wear razortail belt (33% pierce) and have 67% pierce from PM skills, do they stack via addition (resulting in 100% pierce) or via multiplication (resulting in 78%)?

They stack in addition

So 69% from pierce and 33% from razortail

Don’t think 67 from the skill is possible