Another point might be that it is really really difficult to get a good, consecutive shot into a Ki84 once it starts maneuvering.
Had a quick flight today with the Ki-84, and met a Seafire. We went into maneuvering contest and something felt wrong - I was pulling the stick hard, and the plane won't stall..
Then I realized that I left the stall limiter on from testing the 109 turn performances out before. The stall limiter limits the plane to x degrees of AoA before stall - in the MA I believe it is set for 2 degrees.
Well, had no problem beating the Seafire once flaps went into action. This Ki84's as slippery as an eel.