atium burns too fast to be of use in a prolonged fight, and don't forget about the other lashings (arrows and the shield from WoK) painting the floor or other objects with storm light and no mistborn would be able to move, and when all is said and done kaladin could with enough storm light effectively throw a boulder faster than a bullet with enough lashings. a mistborn needs metal every object is a potential bullet to a wind runner, the real problem is kaladin can kill unless he is protecting. mistborn have no checks on their power