Leon is a servicable backup, but that's all he is. The Sox catchers have the worst WAR in baseball, and Leon's a decent part of that. When Pedroia's healthy, Nunez is a bench player. However, Pedroia's only played in two games all year, and nobody knows when he's coming back. So for the foreseeable future, Nunez can't really be considered part of the bench.
And yeah, the pitchers are great. The offensive depth, that's a bit of an issue. The bench is only Swihart, Leon, and Holt.