Yeah, so I similarly had 30 runs of "no outcast is evil",
and then suddenly had one round where 3 bombardier's spawned, and I was like "Okay, so like... 2 of these are fake.... I have to guess which 2" (Everyone else was bakers.)
So... its definitely POSSIBLE for outcasts to be demons, but I agree, I don't see it very often. (Possibly in part because if I have a demon pretending to be a drunk pretending to be a slayer, this is just a demon pretending to be a slayer)