Considering in this particular instance the ruler who clicked the 'exile' option has less H/P than the target, I am going to say this was a large mistake on the rulers part.
I myself have never bothered using exile, as the gains don't outweigh the risks. Thought about it several times in Solaria, and definitely thought about it in Swordfell, but I can't see a situation where it would be a clean break. The exiled person really has no motivation to leave, and plenty of motivation to stay and watch the Ruler suffer.
Luria is a prime example of how to deal with undesirables, there are more ways to chase someone off used in Luria in 12 months than the rest of the game put together for the same period of time. Dukes pose a special problem compared to most, and a royal duke even moreso.
