I was wrong about this movie
After my first viewing I dismissed it as middle of the pack Kurosawa citing reasons like lack of characterization, bad hollywood score, and little dramatic weight. I just watched it a second time and suddenly see what I was missing.
I was at fault before for criticizing the movie for what is was not, instead of analyzing what it was. It really is a great film and deserves to be ranked as top class Kurosawa along with Ikiru, Seven Samurai, High and Low, Ran and Yojimbo.
My biggest mistake was faulting the movie for not having any "exceptional individuals" that other Kurosawa films have. This was a bad mistake because the movie isn't about individual exceptionalism but is more about sacrificing the self for the greater good, in this instance the perserverance of the Takeda clan.
Nakadi is great as Shingen and his double. His transition from a scoffing thief who chides Shingen and his brother for being merciless murders to a devout member of the Takeda clan is truly a sight to watch.
I still don't think the movie is perfect. There are a couple of scenes that might be cut (the nameless lord who reacts to Shingen's death, the recitation of some Noh poem about "live not being forever" by another lord, the dream sequence could have been shorter). I still think that the score is a bit of a weakness but that didn't bother me as much on the 2nd viewing.
Kagemusha is truly a great and unique movie in the Kurosawa unvierse for its stance on the clan vs. the individual.