I have been making repeated runs, (offline), on the tank drones. Soviet heavy rockets seem to work, but American Rockets are literally bouncing off! I can fire them and watch the smoke trial. If I get a hit I can watch the smoke trial as they ricochete off the vehichle. I will try the salvoing and see if that changes anything.
As for the American Rockets. I am not sure, but I am under the impression that the standard Rocket for US planes was the HVAAR rocket, (High Velocity Anit Armor Rocket).