I think tunnel vision is the number one problem on that mechanic. It happens to me a lot, though I'm trying to break myself of the habit. Once you snap out of it, it's pretty easy to see, but I do agree. The color of the shield displays blend into the surrounding environment. I wish the icon had a directional symbol on it. Right and left would obviously mean one of his sides, and an up and down arrow would signify his front or back respectively.