what i meant was, the rasanegan should've reduce the attacking power of chidori, making it less powerful and probably not much of a lethal attack anymore. lets put it this way, lets say a fatal blow has the power of 5.

at the start chidori was a 10 and rasanegan was a 8. After they clash, chidori wins but only has attacking power of a 2 now, which isnt a fatal blow. Get me now? and again, this is just what i think.....