I believe the servitors have been seen in three stories so far: Backup, Bombshells, and Ghost Story. In all three, the Servitors have appeared scarily competent, while the Fomor have appeared powerful but arrogant/stupid. The servitors also have most of their sense of self removed and astonishing loyalty installed, thought that might be unique to the servitor leader we've met. This is a strange combination, to have the servants being the smart ones. In Bombshells we learned that lead servitor was a "pet" of the queen (I think) and not directly subservient to the Fomor present, and even willing to disobey him to further their ends. So the competence of the Servitors may be a reflection of the competence of the Fomor leader, and we might being seeing weeding out of some of the more... questionable members of the Fomor nobility on display so far.