Let's be honest...how are you determining that this field is a joke? Because very few players have a big clay title?
Well, then the field, regardless of surface, is a joke. We have maybe ten players out there with any significant titles (GS or MS) on any surface.
But if you look at who is on top you quickly realize what the rest of the guys are up against. You have two incredible players, who would probably have gone down as at least multi-Slam winners in any era you can name. And then you have their understudies, two hungry, cocky kids who might sneak one out in any era.
There is no way you can call Federer or Nadal average; they have simply been too consistent. No "average" pro could keep up the mental strength needed to wipe the floor again and again and again like these guys have. You look at Djokovic, Murray, and Roddick-the three players who have probably suffered the worst under this domination--and you can see that had the top two not been there, they still would have had to share amongst other players.