Quote from Rydian;1277546:
Your crit - (2* enemy_protection)
If the result is higher than 30%, cap it at 30%.
I don't think that's what he's asking. I believe he's asking how Dual Wielding affects the Critical rate.
Anyway, displayed stats dual wielding averages out damage, critical, and balance between the two weapons. So, if you have two weapons that give you 50% critical, then the stat window would remain the same as if you were using the weapon as a standalone.
However, Dual Wield Mastery adds critical on top of the average listing.