I was thinking about how 2 on 1 works in OP. Prime Harp and Sengoku beat Shiki after a lengthy battle and it clearly took everything they had. Perhaps it's not as easy to overcome a stronger fighter like it might be in DB. I do agree that they can win and could likely give him some trouble individually.
It makes me wonder how Kaido would have fared against the Supernovas without Big Mom on his side. Obviously he'd take out some of them, but I wonder if he would have gotten overwhelmed by their numbers eventually.
I feel like he wouldn't lose. Garp and Sengoku were within range of Shiki and it still took all they had to beat him. Luffy was the closest one to Kaido, and we know he wasn't even close if even his Haoshoku infused attacks are nothing to Kaido.