This is fact. It works especially well on HWGuys and soldiers. 3 Flares Tactics - Be aware of your surroundings. All to many times snipers get too caught up in hitting a far away target that they tend to ignore immediate dangers. Be sure to listen for any noises which could tip you off to an attacker.
Snipers are one of the best classes for taking out sentries.
Unfortunately it's hard to find a good offensive sniper. And 1 Nail Grenade Tactics - You know, splash damage sure does kick ass. So does 200 armor. That makes the Soldier a Sniper-killer. Launching rockets from far away can detour them long enough for you to get within gibbing range.