Was just talking to a mate who used to live in Mansfield and was a high country tracks regular. He said, if you're after steepest but not necessarily hardcore, the deddick trail is the place. Tracks there are smooth but ultra-steep.
Also, for what it's worth. The iconic tracks that used to be hard such as the billy goat bluff and blue rag are now graded and before closures, X-trails and foresters were seen up there where as before that, it used to be a cruiser and patrol country.