Setting the boss's group to "Empty" will only work if the mission enemy group is set to "Empty." You can then populate the map with boss spawns and patrols and such.
Eva Destruction AR/Fire/Munitions Blaster
Darkfire Avenger DM/SD/Body Scrapper
Arc ID#161629 Freaks, Geeks, and Men in Black
Arc ID#431270 Until the End of the World
If you want your boss to be single, have the hot young intern in accounting hit on him, then take photos and mail them to his wife. They'll be divorced faster than you can say "Shoulda signed a pre-nup!" and-
...
Wait, that's not what you asked at all, is it?
-STEELE =)
Allied to all sides so that no matter what, I'll come out on top!
Oh, and Crimson demands you play this arc-> Twisted Knives (MA Arc #397769)
Ok I must of been chewing on a lead pencil for too long because I can't for the life of me get a boss objective to spawn without any other critters. The boss difficulty setting doesn't seem to have a 'Single' option, and when I set surrounding enemy group to 'Empty' the mission's default enemy group spawn with him instead.
The only way I have been able to get a boss to spawn on his own is to choose an Escort objective on the 'Single' difficulty that betrays straight away. Im not keen on using this method as I am concerned about a possible xp nerf as Escort's count as allies.
Can anybody out there tell me if I am doing something wrong?