I do think Zoro used Asura one more time in Sabaody, in Straw Hats vs. Pacifista. (Maybe that was anime-only, can't remember.) Certainly not post-timeskip, though.
I'm one of many who found Nami vs Kalifa unrealistic, because the Kalifa we saw in Water 7 should have stomped Nami. She had a freakin' barbed wire whip in addition to her Six Arts, and was taking out the Galley-La fodder like there was no tomorrow. During her fight with Nami, she decides to not use the whip at all, use the Six Arts as little as possible, and instead primarily go with a brand-new Devil Fruit power that she's only just getting the hang of? Yeah, okay. She also pretty much turned into a "dumb blonde" during that fight, instead of the smart lady we'd seen previously. Actually, that's the problem with Nami's one-on-one fights in general: her opponent doesn't "just kill her already" like they should, but instead dick around enough so that she can beat them. Let's be real here, Nami vs. Miss Doublefinger/Paula was awesome, but Nami really shouldn't have won if the fight was at all realistic. If Paula hadn't just stood there letting her repeatedly screw up with the Clima Tact, she easily could have poked her full of holes. Every time Paula did say, "Okay that's it, I'm killing you now", she gave Nami enough warning ahead of time to dodge all the attacks. When Nami did get the attacks to work, Paula never really tried to evade them, and just stood there and got hit. Don't get me wrong, I do love Nami; she's a science chick like me, and she's really clever and smart. It's just that her opponent always needs to be dumbed down to an unrealistic level in order for her to win the fight.
I'm not gonna lie, I actually really didn't like Luffy vs. Usopp at all. Not because the fight itself was bad–Usopp was indeed quite clever--but because it was so hard to watch two close friends who love each other fighting for real and seriously trying to hurt each other. The friendships between the Straw Hats is my favorite part of the series, so seeing that really upset me. In fact, even though I did read the whole thing in the manga, I skipped the fight itself in both versions of the anime because I just couldn't bear to watch it.
I didn't mind Straw Hats vs Oars that much, but the fight was definitely too long, and there was too much Oars and too little Moria. The enemies in Thriller Bark spammed their moves way too much as well, like Moria's Brick Bat and Perona's Negative Hollows (until they didn't work on Usopp), though I guess that's actually realistic.
I think one of the many reasons I still love the East Blue saga, even now, is that I didn't have a problem with any of the fights there. The strength levels of both the protagonists and the antagonists was realistic, and the fact that there were almost no Devil Fruit users back then meant that, instead of the opponents using a new application of their Devil Fruit to make the fight difficult, we saw clever applications of weapons (like swords, axes, guns, and cannons) instead.
Other fights I thought were bad:
-Nami + Gan Fall vs Hotori + Kotori. As others have stated, that was pretty pointless.
-Sanji vs. Kalifa, too. Yes, Sanji, I understand you respect women, but when this particular woman is stopping you from rescuing your friend (who is also a woman) and she's trying to kill you, it's time to beat her ass.
-Yeah, Chopper + Robin vs. Hogback + Cindry was bad. So anti-climactic.
-Luffy vs. Jimbei. So unnecessary as a fight between friends that wasn't needed, and a failed attempt to create tension.
-A lot of Fishman Island. I didn't mind that the Straw Hats dominated because they were supposed to, but as others have stated here, not the best choreography. I found it all to be extremely forgettable, honestly, to the point where I don't even remember many of the opponents' names.
-The Yeti Cool Brothers fight in Punk Hazard. What was the point of them again?