@I:
@ Brennen–I know you didn't ask me, but we saw Luffy defeated by Ace as a child, had Luffy claim that he'd never defeated Ace, and we saw Ace and Jinbei fight equally before Ace got to WB. By logical extension, wouldn't that make pre-TS Jinbe stronger than Luffy?
We don't know the specifics of the Ace Jimbei battle or why it was so even. And Jimbei has water based abilities, which would be pretty rough for Ace to deal with.
And even after that, there's different strengths and weaknesses. Jimbei can swim and Luffy can't, but can he hit as hard as Luffy does, take hits as well as Luffy does, jump as high as Luffy can, devise battle strategies as well as Luffy does? Etc. etc.
Crocadile nearly killed Luffy twice, but Luffy came out triumphant in the end, so which one is stronger?
Strength tiers in OP aren't so black and white usually when there's strategy and tactics so heavily involved in any given battle, so its incredibly hard to gauge overall strength beyond whatever feats we see on screen. (Zoro tossed a house, so what does that mean?)
Though now that haki has entered the equation…
The only fact we really know is the Strawhats all did serious nonstop training for the last two years. The way they handled the Kumabots is evidence of their massive jump. Now Lufyf is taming giant monsters and Zoro is OHKOing a fishman underwater. How high have they've risen? It'll be a while before we find out.