I dont think his crit rate is bugged. His extremely high damage comes from a couple of things.

1. He's pretty much always going to be a pos1 ninja, and this meta is pos1 stacking, so yeah. He's going to be doing crazy amounts of damage.

2. He does elemental damage. His standard does both Wind and Fire (with 6 paths naruto's running around, Fire is strong against Wind). His chase does Fire, Wind, and Lightning.

3. He has chakra scaling. For every chakra point over 50 he gains 2% ninjutsu. That means if you have 100 chakra, that's an extra 100% ninjutsu. To put that in perspective, that is Ninja God passive from Hashirama (30%), A barrier that enhances Earth Attribute Ninjas (40%), and Konan passive (30%). All of this, by just having chakra. So then you could add those other ninjas to your lineup to boost his damage EVEN MORE.

So thats just normal damage and then critical will increase this damage. If you think this is not the case and that its bugged, just check the secondary stats on their Kakuzu and see for yourself.