As you can see from the table, the average adjusted offensive efficiency ranking for the final four teams has been lower than the defense. The only exception is 2012 when four of the top 8 defensive efficiency teams made it to the final four. So on average the final four has been made up of better offensive teams than defensive. Of course the numbers are based on the entire season and not just the NCAA tournament so a team theoretically could make a run and play above their normal rating.
While I don't think these numbers are earth shattering, I do think it has some significance and givs credence to the importance of being a good offensive team. What does really stand out to me is that there have been only two teams in the last four years to make the final four with an offensive or defensive rating outside of the top 50 (Louisville in 2012 and VCU in 2011). Bottom line you better be very good on both ends of the court to make a serious run at a title.