Ashura? Based on what?
We don't know how strong they are in Sulong form and you should not forget that they 2 vs 1 Jack while he was in his slowest Form (Full Zoan). Kaidou, a Yonkou, is getting speed blitzed the whole fight by much weaker people, because he is using his Full Zoan Form. That just shows how useless Full Zoan Forms are in a fight getting people who are not fodder.
Asura Based on Cutting Jack and his sword while Jack fully prepared, being called Strongest of Scabbards.
Is it now our problem that Oda writes stupid scenarios ? Jack was already getting confronted by Sulong Minks and was getting hit by swords but still didnt go Hybrid and not only that, he fought Inu and neko without Sulong and they were able to hold themselves and even then Jack wasnt able to overcome them, are you now going to tell me he again was going easy ? not using Hybrid is his choice, he knows which form of his is strongest and still chose full form... not only that, Kaido calls Flamingo as TOO WEAK while Calling Inu and Neko as STRONG and its okay to lose to them, that clearly tells how far above Flamingo they are and how stronger than Jack they are
Kaido using Full Dragon form, it doesnt really matter, Jack had already fought with them and knew they were able to hold themselves 1v1 against jack in normal form, let alon Sulong X2 and it was instant defeat