Dragonhelm
Knight of Solamnia
Since Dragonlance is a direct port of D&D to novel form, I don't think you can really cite it as an example of the fantasy tradition in which D&D follows. Also, the only Hero of the Lance who actually goes from "chump to god" (literally!) is Raistlin. The rest are very much on the "dude to badass" progression.
Of course, part of that is the nature of casters versus non-casters in AD&D... but even so, according to the old Dragonlance sourcebooks, most of the Heroes are statted out at 3rd level at the start of the War of the Lance adventure arc, and ~12th level in the Dragonlance campaign sourcebook (which is set after the war). That's what I would call "dude to badass." Raistlin starts at 3rd level with the rest but is 25th level in the campaign sourcebook.
"Chump to god" vs. "dude to bad-ass" is really a matter of semantics. I think what we're really asking is whether a person begins with some experience or none prior to adventuring. The funny part is, you can represent both scenarios with the exact same stats and differentiate it all through story.
Yes, you're right, all the Heroes of the Lance had some levels prior to starting their main adventure in the Chronicles trilogy. In 3rd edition, we statted them up around 6th level (including Raistlin, since he served as a mercenary along with Caramon for a time).
Yet all of them came from pretty mundane origins. Tanis and Flint were in business together. Caramon, Raistlin, and Sturm grew up in Solace. And so on and so forth.
This theme of mundane origins is one that is part of the Dragonlance setting, as stated in the Dragonlance Campaign Setting sourcebook for 3rd edition. It is a theme that can apply to just about any D&D setting.
You might say that your hero is already experienced, but truthfully, I think you would gain more joy by developing his story from that of common origins to adventurer supreme.
YMMV, of course.