"How to defeat a War using shield?"
You can dip into the rage tree for a bit more hitting power. If you have feint going once a round, with called shot, dev power, and brute force/blood drunk you have quite a bit of hitting power. It's not purely defensive or purely theatrics, but you can still run crowdpleaser, and use a shield, and other assorted theatrics skills, and switch between parrying, counterattacking, and attacking under different conditions.