Of the top 15 teams in bullpen ERA from 2011-13, the Braves are the only team on there more than once. Of the top 15 teams in starting rotation ERA from 2011-13, 4 teams were in the top 5 more than once. This isn't exactly a long term trend. In 2011, 4 of the top 5 teams in bullpen ERA were the same from 2010 (Braves, Giants, Padres, Nats and the Yankees had been #7).
It could be just be a blip, with several teams repeating in 2014 from the top 5 in 2013. We'll have to wait and see. If this happens again,
It also could be part of a bigger change in pitching that has shown itself over the past few years. The number of pitchers, particularly relievers, with high strikeout and low walk totals has skyrocketed over the past few years.
This could make it more common for teams to go from among the worst bullpens to the best without spending a lot of money (as the Brewers did last year, going from #30 in 2012 to #5 in 2013). I would be surprised to see more than one team carry over in the top five in 2014. It will be an interesting development to watch this season.