The Best attack of the SK is the Bold strike, but it's a Spiritual attack, you maxed the Violent slice but you must unlock the SOL buff ( for increase the spiritual damage ).
Why i put the Kaioken on they builds? because you must have a Axe with many crit.energy with they gloves, the kaioken can increase your spiritual damage ( but not the bleeding But it is useful if someone has an anti bleed )
Finally I would recommend this to a duel:
1) Mystic attack + stun
2)Draconic curse + Fear ( after the fear steal life )
3) Curse + Violent slice
4) Bold strike
1: You pull your ennemy
2: You freeze him and you debuff him
3: you use the Fear on your ennemy and the LP Absorb after you launch a curse and you stun him with the violent slice
4: You use kaioken