Anarchy League - How often will we encounter rogue exiles?

I was looking at this post and went back to my game saw that I have slained 6 out of 13 :D

Hi

They seem pretty random in their spawning in areas. The drops from the exiles I have killed have been good always a yellow or two, their like the treasure goblins although far more formidable. I am also quite sure I have never fought the same exile twice since that would be silly. The exiles in a party idea I have also thought of, it would be a great mechanic if the exiles only spawned in parties if the players were already in a present party, although these exiles are getting harder as a player continues into cruel and merciless so they would need a lot of game tweaking to make sure they weren't too uber.

cheers