For somebody who is ignorant on the combat skills the Duke possess and only has seen their 1 time clashes, you sure seem pretty confident in know what they can or can't match.
I'm basing their combat skills on their current portrayal; they could show far more than before, they could also have a hidden Byakugan... or their all out skills are still not on par with WCI Luffy, including his G4th - and said character was trashed by Katakuri.
Wrong, you are saying they can match Kata. Burden of proof lies on you. Go on, prove it.
I haven't seen Ashura Douji in a fleshed out fight over chapters, I'll let you know once that happens, so cant tell you whether he can match bound man or not.
Characters like Doflamingo, Cracker and Katakuri needed special abilities to match Bound Man differently; but all of them couldn't match Bound Man's brute strength.
Jozu, one of the strongest Yonko Commanders physically, couldn't free himself from parasite whilst Bound Man easily broke through it.
Ashura Doji is just another punching bag for Bound Man; and he is even a bigger punching bag for Katakuri.
No clue what you mean by exactly.
I simply meant this: Exactly; and yet, according to your logic, Jack~Katakuri?
The main character needed a mid-battle op PU to defeat Katakuri whilst I don't even think that Jack would be a big threat against Bound Man.
The dukes weren't only compared with Jack to hype them up, they
exactly matched Jack for 5 days. Hence they are close to Jack in strength. There is no point to deny this portrayal.
Ashura Doji is truly the strongest after Oden? What's about prime Hyogoro or Denjiro (Kyoshiro)?
It is simple, WCI Luffy is stronger than all of them - and his G4th massively outclasses them in portrayal. And yet, Luffy couldn't deal jack shit against Katakuri, his Bound Man is also known for good speed feats and yet, it couldn't even hit Katakuri once when he regained his FS back. Also, Katakuri's mochi easily immobilized Bound Man which is already an amazing feat by itself.
Yeah, Capone was shitting his pants because of Nekomamushi, and now? The same Bege considered Katakuri to be the biggest threat at the assassination bar Big Mom.
I just don't see how Shutenmaru, the Dukes or Jack are on par with that guy.
You're simply underrating the Dukes.
No, you're simply underrating Katakuri.
How can I answer you with specific details when I, just like yourself and the entire fandom have not see the Dukes, Jack, Ashura in a fleshed out fight?
See? They haven't shown any feats to suggest they can best Katakuri.
And thus, we have to use their portrayal - and they were portrayed to be on par with a YC3 level character.
How strong is their CoA? You dont know
It is likely that Ashura Doji has Ryuo but in terms of hardening, it is rather unlikely that their hardening is on par or even better than Kata's.
How strong is their CoO? You dont know
Their CoO for sure isn't better than Katakuri's future sight lol.
What sword skills do they possess? You dont
How's that relevant against Kata?
The limits of their physical strength? You don't know
The limits of their physical strength are at least less than Bound Man's; and as I said, brute strength is useless if you cannot connect the hit.
How fast are they? You don't
Bound Man was extremely fast and yet, not fast enough for Katakuri.
Even FS Snake Man had problems hitting Katakuri when Katakuri adapted on its fighting style.
Neither do I. Hence we are using bounties.
Using bounties is just wrong, though.
It's like saying Cracker is stronger than Ace because Ace only has 550 million bounty but we can certainly say that this assertion is pure nonsense.
Only have claimed king and queen > Katakuri.
Claiming King > Kata is debatable, claiming Queen > Kata cause of the bounty gap is nothing but nonsense.
i'm lovin it 
using X Bounties against people form different crews doesnt work properly.