One thing that you didn't account for was the fact that the raiden Kakashi used cut through pure chakra, and not only that, but chakra from the weaker tailed beasts (don't really know if that makes a difference, but I thought I'd not it). But the sword of kusanagi not only had to pierce through chakra, but also that was the body as well, which added to the strength of the chakra. Similarly, it is possible that one can assume that the chakra nearer to the body would be denser.
Now whether it would kill the Raikage? I don't think so. Most of the lightning would be canceled out by his armor. I think.
Now whether it would kill the Raikage? I don't think so. Most of the lightning would be canceled out by his armor. I think.