not really there is 2 factions in the wh codex, one is the ordo hereticus (=][=, assasins, orbital strike, =][=orial storm troopers, death cults etc) and the esseiltchery (i can't spell it but it sounds likr that and technically it's the proper name of the imperial cult) (sisters, repentia, preists, arbites, arcos and pentients etc) the fact is that they are 2 different armies and with the exception of the sisters they would not work together (considering hereticus spends most of it's time hunting or "policing" the esaltury).