In 0.8.4 there is a option in menu that sets the count of drones per wave. Also I added a weapon that disables drones in case you don't want to fight one.
0.8.4 is coming today/tomorrow.
What specs do you have? even on my cheap potato laptop I was getting 60 fps in combat, I think the issue is not with the game but with the graphics library, do you have directX10 or 11 or OpenGL latest version? also what OS do you have?