When you think about it, Vladimir's E is just Swain ult on a 3 second cooldown
And Vlad gets to actually cast it whenever he wants! Unlike Swain, who has to stand in 600 units of an enemy to cast Demonflare (and that's if he starts a fight with a soul fragment).
Don't forget he has to have at least 4 "soul fragments" for the ratio to even match Vladimir's E, which are super difficult to get since the chances of your landing on a target who hasn't been pre-CC'd are slim to none.