Another thought is tiering the system. I don't mean just giving names to the tiers, although I think that might be important. But what about actually creating an immortal tier?
Maybe scale down everyone for levels 1-12 or 1-15. Then, once a certain level is reached, power the heck out of all the classes. I mean superhero scale powers for everyone. Make them immortal. Give them things to do like displace other gods or destroy worlds. Stop calling them adventurers, and clearly contextualize that they are not adventurers anymore - they are minor deities, and if not stopped, will eventually become gods.