Thus far I see Dracula and Succubus being top and Maria being bottom. I have to do a little more research. Dracula is pretty strong though. He's easily top tier and has the most devastating specials as far as I can see. So far it seems like:
Dracula
Succubus
Librarian
Death
Shaft
Richter
Alucard
Maria
This is all just educated guesses till I play them more.