The Red Sox won 97 games in spite of having to use their platoon as regulars for a significant portion of the season. They managed to overcome this problem by having the best offense and one of the best rotations in baseball. The problem that you and others seem to be ignoring, is that the Sox will very likely have a downgraded offense for next season. Ellsbury is gone, Salty (lucky season aside) is gone, Napoli is unlikely to repeat his BABIP luck, Victorino is an injury risk, Ortiz is a year older, and both JBJ and XB are rookies who will have their ups and downs.
Because the lineup last year was much more established and you had a lot more pieces to pick up the slack, you could get away with having one of the worst OF defenses in the Majors when both Nava and Gomes played, as well as having three lineup members (Nava, Drew, Salty) who were completely and utterly unable to avoid making outs against left handed pitching. Next year, the Red Sox won't have such a luxury, and that's why what some view as "merely depth" will become "they should have addressed this in the off-season" as soon as Murphy's Law strikes during the 2014 season.
We have beaten this subject to death, however, so let's just agree to disagree. I say they should be guarded with another OF guy who can handle the stick against lefties (like Chris Denorfia) you say they don't.