I don't like the mob thing either but it's how large group dynamics on the internet work (by default). We try to mitigate it where we can but there's not a lot of knowledge about how to do that.
I don't know what you mean by "no value outside of to YC" but I think—in fact I know—that HN has added massive value to lots of people's lives, and not just by providing interesting reading material. I know this because people tell me how HN changed their life, and I also know that HN changed my life (long before I started as a mod).