No amount of excuses can explain how Mihawk could pinpoint Shanks and his crew's location that were partying in random island that apparently is not even part of Shank's territory. For sure not Shanks' usual headquarters though since that random island doesn't even have Red Hair flag on it.
No amount of excuses can explain how Mihawk could know what's happening in Reverie that took place in Mariejois 10,000 meters above the sea, from inside his castle in Kuraigana.
Those 2 are examples of Mihawk's beyond the world level of CoO.