The problem with AI is they become predictable after awhile. Also, if you add them will they be counted as kills when you shoot them down? If not, why both to chase them, they just become moving obstacles that you can predict where they will go becoming unimportant and so will be basically ignored in a fight. If they are counted, that means they will be able to shoot you down. Imagine the cries! "Dweeb couldn't fight me, had to send his drones after me!".
No I don't think AI is an answer. There has to be a reason to defend, or people won't defend. There is no reasonable way to stop a horde. Sure you and 19 of your buddies can cap a base at 15-20k waiting for an attack they may not come. Maybe 20 guys can get together in winged pairs and do 3-4 sector sweeps looking for an attack and another 20 guys can just wait in a tower shooting the s**t waiting to get a report for when to roll where.
No, until there is a way to entice people to defend, the horde will rule the game.