I only play Spec Ops and so far i haven't felt the need for anything else. One thing i'd like to try, if possible, is Spec Ops with just 1 AI teammember. That way i get to keep my exiting outnumbered mission feel and have support of 1 AI!
The mission is different all the time and i anxiously await new missions by Wiper! Randomisation is a huuuge plus for me.