Mihawk will obviously have the best AP feats in the verse, I don't doubt this, i only doubt now that his title puts him above Shanks. I don't think that is Oda's intention.
If you even agree he will look like a monster in the future, with his attack power feats competing for the best ever in the verse, how does then the argument of "can you substitute Mihawk with Shanks/Rocks and this make sense" work?
Anyone can stall anyone, if the stronger character is simply not willing to use more power than needed to make the fight competitive.
Does it make sense for Vista to stall a character that you predict would have one of the best attack power feats in the verse ever? And have this character lumped in with the rest of the shichibukai?
It sounds ridiculous right?
Well, it's possible if the said character massively holds himself back, and his personality is such that he is bored out of his mind and wants to be at peace until a worthy challenger appears to fight him. Note that Mihawk was far far less serious than admirals were in Marineford, and they too were stalled by WB commanders (this also speaks more to how WB commanders were monsters in their own right, compared to Kaido/BM commanders).
If the predictions of Mihawk showing some of the best attack power feats ever come out to be true, would you in hindsight be able to replace Shanks/Rocks with Mihawk and have it make sense? I would guess yes?
I wish Mihawk's personality was different, but it is what it is. This is Oda's excuse for not having Mihawk actively fight against other top tiers, especially swordsmen like Shanks or Fujitora.