Brytenwalda shields suck. When you hold them "up" they are too low to provide adequate cover, when you're not holding block though, they do a better job covering your body. The equipment is from like the 8th century, so it's all pretty terrible.
The main problem I had with the shield bash was that to use it, you hold right click and then hit left click. Well that's how I feint with a shield (while blocking, I hold left click and release). You have to feint against bots in order to get them to open up their blocks (or to get them to block in the wrong direction), so I was constantly shield bashing when I wanted to feint.