I have become leader of the Assassins guild and have been doing the Nightmother quests, and they seem to be very repetitive. Does anyone know it they have just made The Nightmother generate an endless loop of contractors and victims.

Yep, those are endless quests that Todd promised.

Yup. Radiant Story.
But my good sir, this belongs in the Spoilers forum.

Some Mod will move it, I'm sure.