As many of you know there was one major bug in the game that has eluded me since release.
I believe I've finally squashed it and you should always have bosses spawning at the end of each 5 level zone.
Based on what I learned fixing the bug it was a rounding issue that left less than a 1% chance of the boss not spawning. It should be fixed now, but let me know if it ever happens again for you.
Thanks everyone! While I am busy working on blocked and loaded 2 don't worry I will eventualy go back and add more stuff to Rogue Party. It was designed to allow easy additions without having to create all new levels.
Shout out to Coolguy1079 who is likely the only person who has beaten the boss. Even I haven't yet!