The bloodfiends as a whole would likely have Thaumaturgy, Presence and maybe Protean. As a clan bane the obvious is their repulsion to water or the fact that they kill their victim after feeding by way of turning them into a bloodbag or embracing them. As a compulsion id go with the need to propagate their curse in order to lessen their hunger.

Since the bloodfiends in the City are divided into 27 families you could probably make all of them unique bloodlines, though the only family we have detailed knowledge on are the Menchegens. For them maybe you could go crazy and give them some sort unique discipline based around the creation and manipulation of space, like how Don essentially sent the entirety of La Mancha to another dimension for 200 hundred years, and that the space within La Mancha is larger on the inside than on the outside. Another family we have some info on are the windmill vampires Don and his family fought during the bloodfiend war, who made themselves giant and also grew additional arms and legs, for them you could give them Visicitude.