Ended up making Blood Uchigatana + 25 my left hand weapon in my final build, replacing Unsheathe with Seppuku. Then right hand was Rivers of Blood + 10. Doesn't do as much damage with normal attacks as the Blood Uchigatana + 25, but when you have a decent amount invested in arkane the Corpse Piler special attack procs bleed damage hard and has tremendous range for a melee attack. Seppuku is mostly there to make my Corpse Piler special stronger.