Norushen is expected to be a part of the third encounter in the Siege of Orgrimmar that's coming in with patch 5.4. After we cut through the trash, we found that Norushen prevented us from going any further. Apparently, he detected that we were full of pride and said our bodies had to be purged before we could advance onwards.
Our main job here is to defeat the Amalgam of Corruption. It's the elements of pride within us combined into something that we can tangibly kill. If we don't kill the Amalgam within 7 minutes, Norushen's quarantine zone kills everyone.
And how does one about purifying themselves? Why I thought you'd never ask!