The Bashanishu achievement is not awarded when hitting Bashiok with a normal attack with Rakanishu's blade equipped.
Character: Level 60 (1) barbarian
I have tried this twice now, both times without success. I have made sure to hit Bashiok with a normal melee attack. Rakanishu's blade was equipped.
I have read some reports of this affecting other players. I would appreciate some word on this as it is very frustrating to have put in 10 hours of farming for a bugged achievement.
Screenshot of my skill setup & Bashiok: