I don't think that a Slashdot like system is intended to solve the problem that you describe. As I understand it it is intended to provide a uniform measure of perceived post quality as judged by the community in order to allow users to filter out content that has been judged to be of poor or even detrimental quality.
It is not context specific, and not intended to replace a search function that would direct you towards the content that is of interest to you based on subject matter. Again, I think that there are other solutions available for what you are looking for that would improve, or at least augment the current search functionality. One such solution that has been put forth a number of times is a keyword tagging system such as the one used on Flickr that would allow far more refined searches and hopefully as a result better search results. In terms of allowing the content to find you as opposed to the other way around, well, again that's another lengthy topic, but something as simple as allowing users to set up a keyword watchlist might help or at least serve as a jumping off point for further discussion.
I'm not differentiating Blogs, Articles and Forum Threads. But I am concerned with any of these media containing something that might interest me, but not the general public or the group as an entity, and missing it simply because it wasn't "elevated." Then again, I may not grap the finer points of the Slashdot system. There are a articles, blog entries and forum threads that get a lot of hits, a lot of comments, and even praise, which I find medicre at best. Similarly there are those that receive little attention, and are even criticized, which I think are pretty good. How, exactly, does the Slashdot system help me?