The "Rules for Fighting Caine" solely consist of "You Lose."
Caine is supposed to be so powerful, the game system literally cannot model him.
Also, there's the literal part of the Curse of Caine - the whole sevenfold vengeance thing causes any victory to become an instant 700% backlash against the victor.
Continuity Lock Out: As time went on, the backstory became increasingly thick and convoluted. The Metaplot did not help matters. The New World of Darkness was created because this issue began negatively affecting sales.
Continuity Snarl: There were quite a few retcons and quite a few mistakes. It's difficult to tell which is which.
Fan Wank: Several actually got noticed by the authors and mentioned derisively in the canon, among them a male offshoot of a female only Vampire bloodline, and a "pact" or "understanding" between Gangrel and werewolves, undermining the usual state of affairs.
Specific examples in the Old WOD: the Baali and the Sabbat in Vampire, the Black Spiral Dancers and the Wyrm in Werewolf, the Nephandi and Marauders in Mage, the Spectres and Oblivion in Wraith, the Shadow Court in Changeling, the Akuma and Yama Kings in Kindred Of The East... It's pretty much easier mentioning which factions are NOT High Octane Nightmare Fuel.
More specific examples from oWoD: the Nosferatu, the Nicktuku (High Octane Nightmare Fueleven to the Nosferatu), Followers of Set, the Giovanni, the Tzimisce and (to some extent) the Malkavians in Vampire, the Bane Mummies in Werewolf and the Earthbound (and pretty much any high-Torment fallen) in Demon.
Unfortunate Implications: The oWoD has truckloads. World of Darkness: Gypsies portrayed the Roma peoples as having magical powers tied to how "pure" their blood was.
Villain Sue: the Old WOD was often heavily criticised for having incredibly overpowered antagonists and side characters, who had the potential to make the players irrelevant. Samuel Haight was the worst: the books actually told Storytellers to make sure that the PCs don't have a chance to defeat him.