Without any points in spirit but a lot of +mana on the gear I found, I had about 300 mana, and since thousand cuts costs 242 for rank one...
Maybe I could see it being useful if you had points in spirit and mana effeciency, but otherwise it's not worth it having to chug a mana potion every 15 seconds.
But then again I'm a newb and only went through the game just once. Just what I think.
