There's always been rumors of being able to kill bosses with Megid or Hell weapons, but as far as I know, they are all immune to the effect, as well Arrest, Demons and such, otherwise bosses would be too easy.
I believe that the odds of a weapon having Hit ( or any other specific %) don't change by location, however the odds of getting higher percent do, so while for example a DoB from Forest 1 COULD have high hit, statistically a DoB from Ruins 3 has a better chance of having higher hit. But in no...