True. I wondered mostly because of the CP9 and Pacifista fights. Luffy was slightly stronger then Blueno but he was still around his level while both Zoro and Sanji fought oponents that were nearly more then twice as strong as Blueno and could keep up with them. Same thing in the new world. Luffy crushed a Pacifista but he went to Gear 2 before that while Sanji and Zoro each delivered fatal one shots(although I suppose you could argue that both attacks were needed to take out a pacifista)
The thing about Gear 2 is that it drastically increases speed and strength so I can't help but wonder if Luffy's base strength is actually lower then that of Zoro and Sanji
But I am getting out of topic. Anywhere speaking of hax fruits I wonder if actually all exotic fruits(not centered around one person) have the ability to become incredibly powerful. Yes Dolfa's birdcage and Pica's monster man are impressive but are they impressive because of the DF or because of the users who spend decades honing their skills? For example I can see Nico Rodin with two three decades of hardcore training also being able to do let's call it a Flower Cage with her powers extending to the entire city. Or be able to cnstruct a gigantic clone of herself the size of Pica
Luffy doesnt use gear second as much as he did before. He now seems to be quite a monster without using it beside very short moments.
You have to remember that both Sanji and Luffy during their first encounter/ short fight with Blueno - comparable thing with Luffy looking bit better than Sanji.
Back in EL Luffy was around as strong as Zoro/Sanji, bit stronger than them as it was hinted many times. Gear Second given him further boost in everything that was his best tools so to say.
Zoro and Sanji fought Kaku and Jabra while Luffy fought guy that was around twice as strong(on paper) than both Kaku and Jabra. Of course DJ and Zoros Asura were used for brief moments compared to gear second and were enough to completely overpower both Kaku and Jabra in moments.
If you bring up Pacifista situation - Luffy used only gear second pistol to destroy it - a basic gear second move without even CoA hardening. Same with Zoro using most likely basic CoA of his and Sanji using Diable Jambe. Luffy is great in all round fighting, Sanji is speedster with firepower behind both Luffy and Zoro but with much more intelect than any of them aaand Zoro has possibly as much destructive power(thanks to being swords user) as Luffy but isnt as fast as him or as physically strong imo.
If we come back to Pica subject - he was very dangerous thanks to his devil fruit power being trained to perfection - he was able to move in stone fast enough to avoid any of Zoros attacks and he remodeled very big part of island - yet his skills with sword and his CoA haki were not on par with Zoros abilities.
When Doflamingo will be stripped off psychological advantage(Mansherry saving him) and if Luffy will have counter to his string trap they should be almost evenly matched imo.
As for Zoro being impressive against Pica - Luffy would have ended fight with Pica with simply using Elephant Gattling and destruction of entire stone golem.
We also seen that Doflamingo praised Sanji for power of his attacks and he went for the kill against him rather fast using his string trap that looks like his trump card move and then 5 colored strings that seemed to be strings strenghtened with CoA haki.
So lets compare Sanji getting back into the fight after getting slashed with Pica falling to Zoro. There might be smaller gap between Sanji and Doflamingo or any of monster trio and Doflamingo than we think. Sure thing he dominated Sanji but he went very seriously against him and we are yet to see if he will try to do the same thing with Luffy.
After his clash with Sanji, Doflamingo didnt underestimated Luffy in their first clash - he covered himself with CoA hardening armor against Luffys attack without CoA. This means that HE HAD TO protect himself with CoA hardening haki from not CoA hardened hakified punches. He also avoided Luffys Hawk Gattling instead of blocking it as he blocked Jet Gattling before - Luffys attack with CoA hardening was avoided by Doflamingo as it was considered to be dangerous enough to end up damaging Doffy.
So my point is that Doflamingo is not that much stronger than his seats, he is very calm while fighting and has most likely enormous amount of experience while fighting with strong enemies so most of his fight scenes looked like machine is fighting. Though in last chapter when he was hit - it was possibly only because of shock of seeing Law before him after he thought he finished him up.
Doflamingo is very experienced fighter but gap between him and for example Pica is not as big as people make it out to be. He would possibly be already on his last leg even before Gamma Knife if he didnt patched himself up when Luffy landed Red Hawk and then Law his Injection Shot. Its Doflamingos ability combined with his experience and being calm in fights while provoking enemies that makes him such strong foe to fight against, he is not so far over his seats and he most likely is around as strong as Luffy.
Im almost certain that Oda is writing this last battle in a way that will give us impression that Luffy would be able to pull classic win after fight comparable to Luffy vs Lucci if not for Law heavily wounding Doflamingo. It might not be big handicap, just a slight one when fighting but it will most likely end up with Luffy getting rid of Doflamingo in next 2-4 chapters or so without getting as much damage as he was getting against big baddies from first half of story.
This way we will feel that Luffy still didnt shown all that of what he is capable of, he will go not heavily wounded to next island and if allied with likes of Law he has chance of taking on somebody like Admiral or together with Zoro and Sanji he should be capable of taking out one like Kizaru(payback) and that is really something if we look at how young they still are. Oda is making perfect set up for fights with Kaido commanders to be best fights that series has seen.