Tolkien's references to the "failure" of the Blue Wizards are very contradictive. In one place he writes that they failed their mission and started magic cults among the Easterlings instead. Somewhere else I read that they did all they could to prevent more soliders going off to help Sauron, and I'm quite sure that it said that they succeeded, not failed. Well, they couldn't stop the whole army, but they lessened the numbers significantly.
I often wondered why Saruman came with them. Wanted to "see them off"?
