Vladimir is the only member of the Black Rose to not have an interaction with Swain.
Currently, there are three Noxian champions that Swain doesn't have lines for, and those are Kled, Talon, and Vladimir. Kled I can understand, because he's essentially just a weird old man screaming in a field with his pet lizard, and Talon I can sort of see, in regards to how important Swain may find him in comparison to his sisters. But for Vladimir, it seems really bizarre and unnatural.
Vladimir was the one to revive Sion for Swain's use, and unless Swain just went completely out of his way to avoid him through the process of asking Leblanc to revive Sion and providing soldiers for Vladimir to sacrifice(as seen in Sion's teaser animatic), it's evident that they must have spoken or met in person at least once, especially if he's an ages-old hemomancy lord now or something. Why doesn't Swain have any lines for him?
Yes, I'm biased. [vlad-salute]