The Ravens were bad at winning one-score games in 2014 and they haven't gotten any better in 2015
Winning one-score games is important in the NFL. Outside of exceptions like the 2007 Patriots, an NFL team is going to win more games by a touchdown or less than by 20 points or more. It's even more important if a team wants to go deep into the playoffs, as the teams there are legitimate contenders for the Super Bowl and are too good to get blown out (most of them are anyway, looking at you Colts).