If anything, Federer should be the benchmark of an all-round player (and I'm not a Fed fan "primarily"). All-round player should include baselining as well as volleys and especially overheads which Djokovic is not so great at.
He has a great forehand, good enough backhand (of course this is disputable amongst TT...), and great volleys.
Defense and movement are superb though defense isn't quite as good as the other top 3 as far as retrieving is concerned. Fed also has the best offense. When I think of another all-round player, I think of Tsonga, but he's lacking in many more areas unlike Fed.
To me, I see Djokovic as a baseliner primarily. That is what he's best at. At times, he is very uncomfortable at net, and if you want to be called the benchmark all-round player, you better know how to S&V as well.