Prisoners count as civilians so you can dump them on the Paradans, Cardassians, etc. in the DOFF missions that eat five civvie doffs and spit out some dil, a respectable amount of Recruitment CXP, and the normal amount of experience. Of course you have to complete at least one of the Consular/Embassy DOFF chains in Cardassian Space before those missions start appearing (and they only appear in Cardie space).
Correction, those assignments give the smallest possible amount of dilithium that any random assignment can give, and a pathetically low amount of CXP per hour.
I wouldn't run them even if they didn't eat doffs, the assignment slot is better used for something else.