I have gotten 100% voice collection on the English version, Black Orb, but not on the Japanese.

I have found with bosses like Wraith and Barbarossa, it's easier to just get what you can from them and not worry about the more difficult ones. It can take hours upon hours to get every spell out of them (And impossible in the Japanese version, thanks to the Barbarosa glitch). If you get 95% of the Voice Collection, it fills the other 5% in itself.