Well, this has always been regarded as a problem in the NBA... The teams in the Western Conference are generally MUCH stronger than the Eastern Conference. In the Western Conference, a winning percentage of .600 might barely guarantee you a position in the postseason. On the other hand, the Eastern Conference playoff cut is often barely above or on the .500 winning percentage level. But, knowing this, the weakest teams are often the West.
If the NBA were to use a system where out of all the teams, the top 16 overall make the playoffs, I would pretty be certain that the only teams from the East that would make it are the Magic, Cavaliers, Celtics, Heat, and maybe the Hawks. That's 5 teams out of 16!
This is a problem, but the teams are divided geographically... There's really nothing the NBA can do about it unless they switch to a system where the best 16 teams overall make the postseason!