The game's leveling system doesn't correctly up the world level with you. You have too many characters to work with to keep up with the world leveling. They should make it so you can choose which world level you want to play on for people who just want the story, and for people who want to test out newer characters that wouldn't logically survive in high world levels due to not being built right as you get them. I love the game overall but this is frustrating enough that I've stopped playing.