Hit rolls of ‘6’ cause an additional hit. The extra hit is not affected by e.g. Vital Strike.
Humanoid models should generally not have more weapons than they have hands to hold them. Vehicles, monsters, exo-suits and the like might have more. Regular models wielding multiple weapons, such as swords in both hands, add only one (1) attack dice for each additional weapon. In the example Battle faction lists this is already taken into account, and you will find that dual-wielders often have a “paired” version of their CC-weapon.
CC (2)
+1 vs unarmed
+2
vicious
