2002- The Jets, Patriots and Dolphins all finished at 9-7 with the Jets winning the division tie-breaker. The Browns ended up winning a Wild Card spot at 9-7 because they had a better conference record at 7-5 (NE was 6-6). The Dolphins also had a 7-5 conference record, but were already eliminated at an earlier step of the tie-breaker process. So, in 2002 the East lost a tie-breaker to the North.
2003- The Dolphins finished 10-6. The Ravens won their division at 10-6 and the Broncos got a WC at 10-6. The Broncos had a better conference record (9-3) than the Dolphins (7-5). It is worth noting that the bottom two teams of the west were 4-12 while the bottom teams of the east were both 6-10.
2007- The Patriots went 16-0. I'll admit the rest of the East wasn't very good that year even if you take out their 2 losses each to the Patriots. The South earned both of the WC that year. That year the south played the west which sucked as the two bottom teams were both 4-12.
2011- The North got both WC spots. They played the South that year where the bottom two teams combined for 7 wins. This is the second time since the realignment where a division has won both WC spots. Both times, the division they got matched up against was weak.
2013- This time the West ended up with all the WC spots. They played the South who had their bottom 2 teams finish the season with a combined 6 wins.
2014- This was the North's turn to play the South. The North got both WC positions as the bottom 2 teams from the South now combined for a total of 5 wins.
2015- No WC for the East this season. The Jets finished the season at 10-6,while the Texans won their weak division at 9-7. The Steelers got the WC over the Jets because of their cumulative records against common opponents (Browns, Colts, Patriots, and Raiders). The Steelers went 4-1 with their only loss to the Patriots. They got to play the Browns twice and both victories are included in their 4-1 record. The Jets were 3-2 against that same group. They split with the Patriots but had a loss to the Raiders. The Jets loss against the Raiders came one week after their loss against the Patriots. Both games were on the road.
CONCLUSION- Just looking at the number of playoff appearances a division earns can be very misleading when determining how good it is. It is a lot easier for a division which consistently has 2 bad teams to score a WC spot via the second place team having a better record than another divisions second place team. Combine that with the fact that each time a division earned both WC spots they were also paired against the weakest division shows that a bit of luck comes into play each season.