Custom enemies must have the powers included in their "Standard" setting to give any rewards at all, and "High" or "Extreme" to give their full rewards. I'm not sure about the ratio but I think Standard powers in both primary and secondary give 85% of normal rewards (possibly less). If you use custom powers and don't include all of the powers required for the Standard setting, the enemy's rewards drops to zero.
Winner of Players' Choice Best Villainous Arc 2010: Fear and Loathing on Striga; ID #350522
You sure you play the play the published mission, not the local test version?
I`m new to this. However, I published a mission & when I play it the mission gives me no XP. I have a minion, Leut, Boss, & EB types. What am I doing wrong?