I see too many shield players back up. Why? Take your driver's license and pop your S key out of the keyboard. Hold forward, hold block. Take their hit, get right next to them and attack. Keep holding forward and go past them, get behind them and constantly spin around them.
90% of players can't deal with it. In fact your probably won't be able to do it yourself, it's kind of disorienting at first. You might have to increase your mouse sensitivity a bit too. I'm completely serious about removing the S key though, too many people fall into the trap of only moving forward and backward. Only move forward and change direction with the mouse, it makes you move in a crazy snake like fashion that completely fucks people's predictions up.