I actually thought the setting rather uninteresting (vampire overuse syndrome?) and the game was good despite it, not because of it. Sounds, music, visuals, voice acting, art direction, dialogue, just about everything else contributed to the dark and ominous "style". I don't think the game actually needed "vampire" clans to be interesting, anything slightly unusual/supernatural would have done. Just guessing, but I think, like Planescape: Torment, most people who played and enjoyed the game were clueless about the setting and the background before (and after) playing.
But, the style of dialouge was rooted in said vampire clans.