well yea gun powders do magic attack. i always kinda knew that since they attack with a bomb (explosive) instead of a coldsteel weapon or claw or whatever. i don't know about other monsters that appear to do phy attack but actually do mag attack, but those earth magicians and taoists are a pain in the ass for pure str even in garment.
as for bandits, they do a fire attack occasionally but still attack with their blade (i think it's more like the imbue).
darkness status...

i asked that here just a few days ago. they decrease the effect of mp pots by half i think. and the universal pill has a bug so they don't cure darkness.