Using Dominatrix Follower Bosses as custom enemy?

I want to use one type of NPC for the whole spawn. I see that I can add them to a custom group but it seems like I can't use them alone without getting minions and lt's. The powers they use fit the theme of my mission, using only bosses makes it just hard enough to give a challenge at any level without being easy. Having the minions and lt's makes things too easy.

Any suggestions?

My suggestion: don't do it.

A mission with all bosses would be too similar to the farm missions and exploit issues raised by Positron lately. Your arc would likely be flagged for GM review and probably pulled each time you put it up. Forget making your missions a super-challenge; the Devs say its for storytelling, and in essence go on to say say a story with no supporting cast is not a story at all.