I feel that people are taking the exchange between Diamante and Doflamingo too seriously for the whole "genius" thing. He had a cool power which we got to see some neat uses, but besides one line we never got anything to actually back that up. If anything, he was shown to be a troll before we got to the actual Kyros V Diamante fight. He lied to Bellamy's face about having one more chance to redeem himself, which Dellinger was loving rubbing that fact in. He taunted the fact that he killed Rebecca's mom in her face while laughing about it. In the flashback he had the selfie moment while ransacking a place. He was laughing at Senor Pink when he initially got his new attire. Most of all, he decided to keep shoving his dickishness in Kyros's face by trying to attack Rebecca instead of him.
You can complain that he looked weak, and that having Sabo and Burgess in the ring with him didn't do him any favors. I liked the idea overall, but not exactly good for hyping him. Speaking of that, that was where the evidence came in that he truly wasn't a genius, and Doflamingo was just flattering him. An actual genius wouldn't put the actual fruit in the ring. Diamante was a cocky asshole, and he stayed that way. There were some fun moments in the fight, and I was overall satisfied with the fight.
As for the rest of the crew, I was fine with it overall. Dellinger is one I liked overall, but the ending wasn't the most satisfactory. You have someone who took out a number of gladiators, and was a half fighting fish. He was on a roll then taken out by one hit by Hakuba. In some ways it was nice, you have a member who was quite good, and a moment of being unaware can cause your downfall. It was also a nice way to showcase Hakuba overall. That said, Dellinger felt like a member who deserved better in the end. Gladius was a fun fight, because of how he used his power combined with Bartolomeo. The fight with Sai and the old guy (his name escapes me at the moment) was pretty good for a one chapter fight. Machvise wasn't great by any stretch, but I liked it. Senor Pink and Franky was great, with little tidbits here and there, and the chapter ending the fight being great with a heart breaking backstory. The sniping moment was downright awesome, and despite what others think, I liked the first Sugar moment (even Usopp running in fear).
Pica I thought was done quite well overall. I still wished he was a mute, because he seemed a bit more horrifying not talking. I like how he in some ways affected other battles and gave Zoro trouble not through pure power, but just in the way his power worked (I still chuckle how people thought Pica was down from that initial hit early on). Zoro having to use his brains to get a hit in instead of just relying on pure power to get through a battle was satisfying. Sure, Pica in the end wasn't a huge powerhouse, but it was obvious to me that in a direct conflict Pica wouldn't stand a chance. I also liked how Zoro made Elizabello use his strong ability for clean up duty.
Trebol was the only one that I was truly disappointed in. I knew he wasn't going to be a power house, but I was expecting something from him. If it had been a 2 v 2 against Law and Luffy, with him eventually getting taken out like that, it would've been fine. Instead, you have him on the sidelines the whole time, and when he comes out to do something he gets taken out easily. I can get behind how he lost, but I wanted him to do something.
I wouldn't place any of these fights as best ever, or even in the top 10, but they were good overall. Since there was a lack of hype overall for most of them, I can't complain. In the end, Doflamingo was the only one that was hyped up through the arc, and the fight reflected that quite nicely. I still stand by the idea that it wasn't nearly as great as it could be, since it lacked moments of both sides being even. Compound the fact that once Gear 4 came into play, Doflamingo couldn't make a come back, it felt a bit lacking compared to earlier fights.
I'll need to reread the arc to make full comments on other aspects, but in the end, despite some minor and one major flaws, the arc was quite good. I wouldn't put it above the Water Seven Saga or Paramount War, but I could put it above Alabasta.