Star-Lord

Aside from specific card suggestions, I have to say that in terms of deck composition you might suffer from some consistency issues. Having only 2 of a card in the deck means you are at least likely to see it once in the course of a game, but 1/30 means you might go the entire game without it. For that reason you should try and at least consolidate your plot twists; I'd probably drop Best Offense and Savage Surprise so you can get 3 or 4 of the more significant effects like Even The Odds and Earth's Mightiest Heroes.

I also think you should think hard about what you want from your supporting characters: I can see that you're going for a strong Guardians/Avengers blend, but you should be looking at how that conflicts with what your deck is trying to do. From the look of it, you're trying to use Star-Lord to accelerate your curve, and Mantis and Nick Fury can both help with that. However, Nick Fury also requires the same resource as Star-Lord's primary super power, which means you may not always be able to put both to good use. What's more, his stats and the fact that he's the only ranged Avenger in the deck means that unless you shove him into the front row he won't be contributing much to combat.

I have a few examples like that line of thought, but I'm not gonna drop them all on you. Mainly I just want you to look hard at all the card choices you've made and their quantities, and think about just how much they're helping you achieve your deck's goals. I will say this though: don't be afraid to splash a third faction for a couple of slots. With Star-Lord's ability to ramp, dropping a strong solo villain like Sabretooth above your enemy's curve can be a very strong play, even if he'll never be able to team-attack and doesn't enable any plot twists.