Jedi Assault Droids were the rarest droids in the Cylon Imperium, and were never used on a standard battleground. They had one single purpose: eliminate enemy Force-users. These droids were expensive and difficult to produce, mainly because they required lightsaber crystals in order for their main weapon to work. These droids also had the most sophisticated processors in the history of droid manufacturing, making them borderline sentient.
Though a single Jedi Assault Droid posed little to no threat to a trained Jedi Knight, a group of these could be very difficult to destroy. It was considered very rare to see one of these droids alone.
A majority of the Jedi Assault Droids in the Imperium were destroyed during Darth Trayus's invasion of Cylon space. Those that survived became the foundations to an upgraded version, and were shifted to a support role for their successors.