Oda may be introducing this "douriki" bit specifically as a lesson in rankings, saying that numbers and statistics mean little in the long run because they can be outmatched by tenacity and willpower. Then again, hasn't he been saying that all this time?
Another kinda-sorta-semi off topic comment: I hate the shounen manga staple of power levels so much that it's one of the things that kept me from getting into the Naruto fandom. The practice breeds so much CRAP. I see people trying to bring it into One Piece (you know which threads!), and I just want to punch them through the internet for attempting to integrate such a piss-poor comparison system into the fandom. Bless the mods for nipping that junk in the bud, by the way. At least I have enough self control to avoid those threads, or else I'd have been banned months ago.