Here's the issue. On the english servers, thee do treasure has been changed so that it drops at the same rate as the others, and so I'm not sure whether or not that will be implemented from the get go for your servers. Either way, the rate isn't significantly higher, and there's no real good ninjas in the edo treasure. In my opinion, you're better off spending those seals on the Jinchuriki treasures and getting your self Roshi and Han, and still pick up a number of itachi frags while you're at it.