If you want to solo with an overlord...well, you want as many minions as you can.

Skeletons, Mages, Revives. Don't really need to max the skeletons though, if you want, go with Mages and Revives.

What I usually do with with overlord is...I'll get a thorn hireling from Act2, and use AMP dmg on the enemies. So it's not exactly what most overlords do, but it is easy to kill any melee.