peddroelm's post in v591 do elemental bonus talents apply fully to grazes? was marked as the answer
why would it be halved ??
Base_Roll *(1 + 0.2 - 0.5) <> Base_Roll * (1 + 0.2 ) * 0.5
additive <> multiplicative
(hit quality damage mods are additive for weapons and most spell damage calculations -- only one case I'm aware of them being multiplicative for the protagonist AOE burn drain ability)