I assume it's linear. But is it "strictly" so? For example, a theoretical skill of 0 does 0% of weapon base damage, a skill of 15 does 15%, and a skill of 100 does 100%. Or is there some kind of baseline, so a theoretical skill of 0 still does like 25% of damage and a skill of 15 is appropriately in between 25% and 100% weapon damage.