Elise fits your theory of a Black Rose to the t. She's a manipulator, betrayer, and she strives to achieve her own perfect utopia of eternal beauty while solidifying her house's power in Noxus. She flat out convinces people to be her followers and leads them to their death on the Shadow Isles.
Vlad and Swain are extreme shadow areas at the moment. Vlad is so old, and his lore and things so antiquated, that there's not much of him that's even remotely caught up to how they're starting to portray him in the current lore. He clearly helped resurrect Sion with a coven, and nothing in his voice lines or lore would even hint that. He's due for an overhaul in lore, much like Swain, who got a lot of weird and interesting new tidbits with the Vastaya connection. I think Urgot will (finally) usher in the second half of the Demacia/Noxus event page, and give us the lore overhauls we need for Noxus.