It seems strange to me that it took Karin that long to figure out where he was. I was under the impression that it didn't take long at all.His original intetions wasn't to attack all the Kages. It was because of Zetsu that he had to fight, And that was only to buy time for Karin and test out his MS. Once she located Danzo and he succeed to use Susanoo, He left to complete his mission.
And you know what? Danzo probably is the most powerful Kage. Because he has THE SHARINGAN IMAGINE THAT