I think good one-on-one defenders are just the icing on the cake of good team defense.
Boston has KG and Rondo, who are good one-on-one defenders, and many average defenders. But as a team they play D really well. The Celts are well-known for being able to load up on a team's strong side and to shut down or bother the first option. That gives the Heat a lot of problems, as the so-called Big 3 are often on the same side of the floor. If you go to your weak side, the Celts are good at recovering and covering that too.
The Lakers are the same way. If you beat their perimeter, you're likely to face one or more 7-footers on your way in. Plus the Lakes are able to play good D without committing a lot of fouls. All PhilJax championship teams have played good D this way, no matter who the personnel were.
In both systems, players have come and gone, but team defense has been the norm. To punctuate this, note that Artest is no longer the one-on-one defender he once was (rewatch the Finals again and see Paul Pierce having his way most of the time) but the team covers for each other well.