The following six teams are top ten in the league in both offense and defense, ranked by average rank for both offense and defense:
Avg. Team (offense rank/defense rank)
4.5 Los Angeles Lakers (3/6)
5 Boston (9/1)
5.5 Detroit (7/4)
6.5 Dallas (8/5)
7 New Orleans (5/9)
8 Orlando (6/10)
[editor's note, by Jake] Thanks to Wes for noting I forgot New Orleans, which made me realize that I actually mixed up some of the figures from this year with last year. The list is now fixed above. Also, I forgot to give credit here. The statistics are efficiencies from the great stats page on Knickerblogger.net.
Here are some rankings from other teams. Note how many of the teams we think of as powerhouses are one-dimensional:
San Antonio (12/3)
Finally, as far back as I looked (2000 season), no team that wasn't ranked at least in the top ten in defense and at least top 11 in offense has won the NBA finals.