Add an alternative attack option for claim parts aka. DrillController, that makes the casting creep immobile and unable to be healed until it stops drilling for 20 continuous ticks, but does a LOT more damage to controller, like 5-10x as much as attack controller.

If you have complete control of room it will allow you to take out controllers much faster, but if the enemy has even a few turrets operational he will be able to take out the drilling creep no problem.

Alternatively, give attack-controller a range of 2 (or 3) so an attacker willing to shell out the energy can mass more of them.