Part of the blame must go to Des. He's obviously not smart enough/good enough to offload a football, so why play him as an edge running forward? Stick him on the bench and have him run it straight for ten minutes a half. It's all he's good for.
Williams did some good things and caused Souths line some problems when the rest of the Dogs pack were very ineffectual, but yeah he was comically bad a lot of the time both in attack and defence.
Some of his runs were pretty good, he just can't be allowed to pass at all. I thought the one close to the line with Morris was acceptable as a mistake given it was maybe worth taking the risk but combine it with the other attempts, it's better off just telling him to never pass no matter what.