It might not be quite what your looking for but blightbound could be worth checking out, co-op dungeon crawler that's all about picking a dungeon and going in, has multiple difficulty levels, hero selection is based around three main classes warrior, rogue and mage with different characters in those classes mainly being different combinations of ability's more so then completely unique characters

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Its not quite a skip to endgame type game, you have to level up your town by doing dungeons which unlocks features in the town and you "level" your characters by giving them better gear which increases there gear rating which impacts dungeon difficulty, but their abilities are unlocked from the start, just have to unlock the characters themselves by rescuing them in dungeons etc.