Is like that from when i started thegame, the offensive stance give 1 attack roll for 0 def that's how is supposed to work.
What is weird is that for melee class that's mean lose their defensive roll, but that's not for ranged class because they don't have def roll also if in "normal" stance.
Surely use of this stance on ranged is way more efficient that for melee class. I'm not sure if that's intentional or take into consideration by designer but is how it work from the beginning.
Honestly i'm not sure if i like stance or not, they seem to bring some exploit in some situation, but army base stance give some nice diversification.... dunno prob it's ok, but would be ok also without stance.