Unless you have a lot of H/P to be waste on exile someone, do not use it often ever.
There, fixed that for you.
Exiles are rarely every useful. I've never used it, and I don't see my self ever using it either.
If they leave your realm--step outside your lands, I think, due to the "within the realm" phrase--then they become rogues.
That wasn't my interpretation, but I would really like to know if that is true.
Not even a little bit.