But that's exactly the point. Akatsuki is not greatly outnumbered. Half of them out be killed by their stronger counterparts. It's not like Akatsuki won't know there up against 18 shinobi. They'll go after the ones that are easy pickings for them first. For example, Kisame will clean up Chojuro. Sasori will clean up Kankuro. Itachi will kill Danzo (he already has beef with him anyways), etc.
The only shinobi on Team Kage who would put up a decent fight would be the 5 Kage and maybe 2 or 3 others. Nagato alone was able to handle KM Naruto and Bee. Kakashi was killed by Deva Path alone. In a real "to the death" battle both Naruto and Kakashi would be at the mercy of Nagato. Even they wouldn't be included in the main showdown.
It's not going to be one on one for each fight..it actually equals out to 2 on 1 in the Kage's favor.
I mean I can easily say the Kage team takes out Akat by saying:
Raikage is far too fast to get hit by Sasori, gets behind him, destroys him. Puppets taken care of.
Kakashi has completely knowledge of Hidan and is the superior CQC fighter. He can take him out pretty easily.
Naruto in sage mode can take on Kakuzu, and if he gets in too much trouble, Kakashi can get rid of Hidan easily then assist Naruto.
Oonoki will have no issue with battling Deidara. He's more than fast enough and his justu can take out the strongest of opponents.
Kisame isn't going to turn the battlefield in to water, he'll kill his teammates, so he's pretty hindered here. He's still skilled out of water, but not enough to compete with someone like the Raikage after he kills off Sasori. Someone like Darui can fight with Kisame up until Raikage gets to him.
Mei can melt Sussano, so Itachi may as well not even bother with that.
Gaara can just stall with defense against Nagato til he can get some assistance from the rest.
Tsunade can deal with Konan. Without her sea of paper, there's not much she's gonna do.
That's only using 8 of the Kages team.
Yes, I completely realized what I said was unrealistic and wouldn't happen in a "real" naruto fight. However, if you're going to use the whole "well this one on one would go this way", I can counter just as easily.
Also, in the response to the 30% fights - Lee and Neji got trapped by an extremely simple technique, and was just a plot technique to let Gai show his skill off vs Kisame. Nothing more, nothing less. No one here is going to get trapped like that.
Itachi's clone didn't take on Kakashi and Naruto with ease. He got Naruto in a genjutsu, but if anything like that happens here(and I doubt it would), there's plenty of people to knock the person out of it. Kakashi didn't struggle with that Itachi at all.
We didn't even get to see Kakashi at full strength vs Kakuzu. He had to take the electrical blast to save them. A full strength Kakashi, especially with his stamina increase to this point would give Kakuzu a run for his money. Sage Naruto took out all but 1 Path of Pain..he can take on Kakuzu too. And he'll have help there if he needs it.
Nagato presents the biggest problem here. Everyone else in the Akatsuki group has a matchup that is extremely unfair for them/or is in a situation where they can't fight to their fullest. Sasori can't poison someone he can't hit in Raikage. Onoki can fly just as well as Deidara. Kisame can't use his Shark Dance technique unless he wants to kill his team as well, and while he's still formidable without it, he can be taken down. Mei can melt Itachi's sussano which would hinder him greatly.
Hidan can't beat someone who is better at CQC and has knowledge. Konan doesn't have her sea of paper. Kakuzu fighting Sage Naruto would be difficult, but others can help Naruto if he needs it. But given what Naruto showed in sage mode, he might not need it.
So long as others can hold off Nagato(like I said, Gaara can play defense for long enough), you can argue the Kage team dominates this fight, as everyone will just gang up on Nagato at that point.