Enjoyed similat success with my droids. I agree with the AoE angle - it's the only to stop those roaches coming back and overwhelming you. But the main key is to always (always) target the Scouts and Warriors first. They're the only ones that do any damage. Even if you've nearly got that Elder down, take your time and slot that little furry sniper that just popped up. It's a bit of a grind but it's the best way to stay on top of the tide.
Here's a vid of GG and the boys cleaning up. They've all got an AoE and you can see how effective it is:
https://youtu.be/zdFuRIfAuss