I think it's balanced by the fact that recon is pretty much done for in close range if they miss. Plus, if you're assaulting and expect CQC you'd be packing buckshot instead of an AR.
It often takes longer in basic modes (non hardcore) usually to take someone down with buckshot than with an AR sadly unless using an auto shotty which many don't have unlocked. Frankly I would prefer slugs which up close are pretty much instant kill. Most people want versatility in combat though, shotguns are highly limited while AR/Carbines are viable short to medium range so they work perfect for assaulting.
But in the same token, the Recon players all have access to the same shot guns also in a CQC situation, they have access to many unlocks that are good at multitudes of ranges.
Recon don't need their sniper rifles being viable in CQC, they just need as a class more of a role in that situation to make it useful for the team. A recon in a CQC battle has little benefit to the team, their class is more designed for larger more open maps. Buffing the effect of their rifles doesn't do much to help the team while the other classes have actual roles that benefit the team and others in those close quarters battles. Sneaking in and placing spawns are helpful, but as been complained about by other Recon players, you get crappy points for it compared to the other support abilities of the classes, hence they should increase the points gained for recon abilities to compensate