This deck is surprisingly very good. I just recently pulled Darkhawk and thought of trying him in a different "unique" type deck. It's really fun with the turn 5 Captain Marvel followed by Doctor Doom.
The essentials in this deck are the following: Darkhawk, Korg, Rockslide, Doom, Mystique, Psylocke / Zabu (if you bought him), Black Widow.
If you do not have Goose, Storm works really well, followed by Jessica Jones. Beast and Scorpion work wonders as well as a good 2 cost. If you don't have Rescue, Shang-Chi and Spider-Man work great. (Zabu also makes this deck superb, but since I'm f2p this is a Zabu-free list)
If you do not have Marvel, Aero and Sera work as wonderful replacements for her. Devil Dino and Doc Ock also go great there too.
Have fun with this deck, good luck on the ladder.