The leather shoulder pauldron you are referring to is more than likely the armor used by the archers. Ninja wore very little armor, and what armor they did where were taken defeated samurai. Light chainmail was utilized underneath or only specific parts, usually from the foot soldiers, were used to protect enough, but not too much to hinder movement.
I have some samurai armor and ninja armor myself (replicas). I was actually going to try to go to my local convention in my samurai armor, but with the Predator features.