If you use an MFR Spawner and use conveyers into a autonomous activator with a Beheading Sword (Paper/Thaum with max beheading and a flux upgrade) it will automatically kill them and drop their heads most, if not all of the time. You can then have a servo set up to pull out the sword when its at a certain energy level so that it pumps into a Energetic Infuser, which will charge it, which you can pump back into the activator. Its a pretty easy setup, and works wonders!