I feel as though I'm the minority here, but in the round of Medium Co-Op with the AI that I played on map #2, I was able to win.
The only real close call I had was wave 3 when I hadn't teched up yet to get a second servo but my turrets were able to hold it together.
I think the big deciding factor here is whether your servos are ranged or melee.
I had a rifle, a twin pistol, and a twin piston servo, and once I got to the later round the piston one was dying extremely quickly or getting stunned over an over before it could do much, but the ranged ones were doing just fine.
My main tactic was to get a couple factories down and then use the drones as meatshields while everything else shot the spawn.
