Last 8 games of last season, we started a combination of Doughty/Gomes/Barnes at the safety spots.
Was it pretty? No, but it also wasn't the primary reason we went 2-6 in those games. The safeties (yes, even Landry and OJ) sucked last year and they'll suck again this year. We are no worse off on the back end than we were for the majority of last season (one could even argue that 2nd year Gomes and the corpse of Madieu Williams are marginally better than 2011 Doughty/Gomes).
Meriweather (and even Jackson) weren't ever going to be the difference between winning and losing this game. Like NLC said, limiting Brees is all about pressure. If the front seven doesn't do that, it won't matter who is at safety.