vicious stance is made for skill damage only. no general normal critical hit with an dagger or an Bow will count by vicious stances damage up, thats how it should work. And yes, C3 also have Critrate = landing rate. Means 1000 critical rate (maximum on c3 – even on official) 100% critical rate = Every Blow skill of an Dagger will land, even backstab from the front side.