bought a blasting wand while dead, could not undo

I'm not too sure about this, but it's my theory. Rito calculates damage on application, which is why Exhaust can reduce dot's after they've been applied(I.E. Cass poison). If you had malefic vision on a target, regardless of what it is, and buy something that amplifies malefic vision's damage, that effectively changes the state of the game as a result of purchasing the item, making the item non refundable.