Well, being an exterminator means that you need to bring the right tools for the job. In this case, big spears, heavy armor, and automatic weaponry. Taking down one sandwinder... Easy. A pack? Whole other can of worms. They use the dust and it's conductivity to discharge massive amounts of electricity. Hence heavy armor. Their skin is tough, absorbing impacts from bullets, hence the spears. Then the bullets finish them off.