You underestimate plate, even regular plate can take 160+ pounds of force and only be dented, also Plate is designed to reflect projectiles away from the face, they have v shape pattern on the chest to guide them, again Tod's Workshop on you tube has a great video on this arrows vs armor, I highly recommend it. Dur-aluminum could crack it, but this plate will (probably) regrow before the Mistborn can get the next hit in.