Bee has the Hachibi , but Gai would still be too fast for them , Don't see how Bee could hit Gai with a Bijudama , Hirudora & Akasajaku have a better chance of hitting Bee , IMO .
Gai could anticipate movements of a ninja by looking at their footwork(can't recall exact page; but when Kisame-Itachi came to village in part 1 and Gai came the aid of Kurenai-Asuma-Kalashi); so he is good at perception and understanding attack patterns.
Also he was able to handle drunk Lee and he was said to be very unpredictable at that state.
And in Obito fight he was matching Obito with gunbai and intercepting attacks / weapons from different directions.
True but it has been stated many times B's fighting style is unpredictable and different, if Sasuke, a sharingan expert couldnt predict idk how Guy will.
Correction: Sharingan did read them, Sasuke just couldn't react.
Besides, Sasuke hadn't even fully recovered from the Itachi fight.
OT: Gai, high difficulty. The nunchaku's flexibility radius matches Bee's unique Seven Swords Dance with Supervibrato swords.
The thing is, Killer Bee very quickly turns to Hachibi once he starts to find the aforementioned swordsmanship's usefulness limited whereas Gai, in this scenario, has the strength, speed and stamina to endure what would be a very long winded battle between these two beasts:
Last I checked, Guy kicked the shit out of Kisame's duplicate back then without even going all-out.
I didn't know Kishi made any changes to that fight later on.
Oh well, look at this, nothing was changed in this fight after all. Weird, huh. Lol