Are you actually claiming that when a protagonist has survived "too much" crap, or shown "too much" competence, he has, by definition, stopped being human?
"Normal Humans" aren't fantasy heroes.
The two concepts are mutually exclusive.
If you're a fantasy hero, you're not just a normal human, no matter how many tortured paragraphs are dedicated to your supposed normal humanity, no matter how often you say "I'm just a guy doing a job, folks." As a fantasy hero, you will do things that normal humans could never do.
If you are a normal human, you're not capable of being a fantasy hero, no matter how much money, time, practice, or madness you have. No matter how dramatic your history, no matter how lofty your dreams, no matter how idealized your future, you will never be a fantasy hero, and you will only ever do things that, while they may be impressive, are limited by forces beyond your control.
This is the difference between REALITY and FANTASY.
D&D warriors have been forced into some elite version of the former for most of their history; D&D wizards have only ever been the latter, because magic, by definition, makes it a fantasy.
The balance has been handled in literature by never really making the mistake of presuming that your fantasy warrior needs to only perform things that talented athletes can do while simultaneously letting your wizards grant their own wishes and forge their own demiplanes and go to heaven for a weekend's vacation.
So even if your D&D warrior is just "some farm boy," he should be capable of killing dragons, saving princesses, surviving volcano dungeons, rising from the dead, eating the heart of a dragon, cutting down mountains, standing strong against a million arrows, being a destined savior of a cursed town, wrestling a river, being invincible, receiving gifts from gods, taming tornadoes, killing Superman, and picking his teeth with the bones of the gods while sitting on a throne made of the skulls of all who dared oppose him.
Because while he might say "I'm just a farm boy, folks!", the fact is, he's not a farm boy, he's a fantasy hero, which means he can do more than
climb pretty good if he's lucky. It means he gets to do things that no normal person gets to do.