Found this thread through a Google alert. It's funny, as I actually wrote the post you mentioned. Thanks for reading.
I am looking at your Google Page Speed report and your browser cache seems to be configured correctly for the URLs and assets on your own server. The URLS you are looking at in the Page Speed report are all external. As far as I know, W3TC only caches URLs on your own domain. I have been looking for a solution as well to cache external URLs, or at least make period copies and cache those. If I find anything, I'll make sure I post here.