I think they were jonin not chunin.Really, she countered sasori, sasori had the hype, and besides she has the seal. Sakura can solo him, hell Tsunade can too, the Sannin were probably barely chunin fighting him. They weren't strong until they split up
They can beat Hanzo since Sakura can counter the poison, has the slug and Lee can go 6th gate. And Hinata has the Byakugan so she can sense Hanzo and his salamander should he hide, plus her Byakugan attacks with some chakra from Sakura should do some good damage.