This is updated from the one I posted in January, with a few minor tweaks to old ratings for better consistency and Vengeance heroes added in. I will update this again with my Cosmos ratings once that expansion is released.
Again, this is not a "Which hero is best" exercise, but an attempt to show where the strengths and weaknesses of each hero lie.
4 overarching categories, Offense, Defense, Support, Mechanics.
Each of those was then broken into 4 sub-categories, and those 4 categories where each given a 0-5 score, adding those up gave the overall for that category.
Note there is a second tab adjusted for Promo Character Cards.
Here's an explanation of each rating category so you can see how I judged them.
Offense:
Relieable damage: Given 2 cards in play, how many different combos deal damage, and how effectively (early game and small set up)
Damage Boosting: increasing damage dealt, yours and others (bonus for boosting more heroes)
One Shots: Damage dealt by one-shots
High End Damage: With all the cards you could want, how much can you throw down over several turns.
Defense:
Damage Reduction involves reducing damage taken by heroes
Damage Prevention involves reducing damage dealt by villains, being immune to damage and redirection away from heroes.
Healing is recovery for you and others
Tanking is redirecting damage away from a hero to a different hero. (usually yourself, but smoke bombs is also tanking)
Support:
Destruction: How much destruction the hero has, Environment and Ongoing, how many cards do it, how reliable is it, how much cost for doing so.
Ally Card Help: Putting cards in other hero's hands or in play.
Synergy: How well this deck makes other decks better in ways not already covered.
Deck Manipulation: Messing with non-hero decks ability to play cards, or what cards are in those decks.
Mechanics:
Search: Cards that pull cards from your deck or trash, and less reliable extra draws.
Base Power: If you have no cards in play how good is your power? (sucks to be AZ, Adept or Unity)
Card Draw/Play: How fast you can draw and/or play cards in general throughout the game.
Internal Combos: How well the deck interacts with itself in ways not covered already. (things like Legacy Ring, chaining Instruments etc.)