Guy doesn't even need all 8 Gates. And being restricted from anything above Asa, (assuming he's aware of such restrictions) I doubt he'd go that far anyway, especially considering that after using it he, you know, dies. It'd be a waste of Guy's life against opponents that are frankly unworthy of having that power used against them.
That said, though, I think Lee and Guy take it low/mid-diff without Guy's 8th Gate, and absolutely no diff with it. I can easily see Lee and Guy tanking any kind of Gentle Fist palm strikes, even with Lee at 5th Gate. Lee and Guy are overloading their bodies anyway, so any "internal damage" caused by the Gentle Fist is negligible, at least until after the battle.
The Rotation might work against the first approach, but it's a pretty poor keep-away against such fast opponents who can get right back up and right back in with no trouble. Same goes for a reasonable Air Palm. A large scale Air Palm Wall like Hiashi used might do some damage, but I'm sure it takes at least a second to gather enough power like that. A second that Hiashi just doesn't have when fighting against Lee and Guy. Plus, I'd say an APW on that scale is most effective against giant, slow opponents, like the Juubi's tail, not blindingly fast opponents like them.
They might stand a chance against Lee alone, but I don't think Neji or Hiashi (even when buffed with BM cloaks) has any answers to two Eight Gates users. I won't even get into Guy using the Gate of Death. Like I said, Neji and Hiashi aren't worth Guy's life.
