Here's my opnion on the "leaked" DLC fighters:
Joker
Despite not being that much of a Persona fan I'm excited for him. He'd probably have an interesting moveset, especially if he uses multiple Personas. He also looks really cool.
Erdrick
Not much of a fan, mostly because there are many other Square Enix characters I'd like over him. If he really is the next character, I'll just wait and see if at least his moveset makes me interested.
Doomguy
Not a big fan, but I see how he could be interesting. If his moveset is cool, I think I might buy him.
Ryu Hayabusa
Not too familiar with Ninja Gaiden, so I'm not exactly interested. I don't know what kind of moveset he'd have or how he'd play. Because of that, I'm not sure what to think of him.
Steve
I dislike anything related to Minecraft. I don't like the character, nor the game he comes from. If we get a Microsoft rep, I hope it's at least Banjo (even though I also don't care that much for Banjo, but he's still more likable than Steve).
tl;dr, I think Joker will be cool, I'd buy Doomguy if he's fun, I'm neutral to Erdrick but I'd like other SE characters better, I'm not too familiar with Ryu and that makes me neutral towards him, and I dislike Minecraft as a whole.