Even in sub 50; if you know what you are doing you can kill a sniper pretty easily with any class so long as you have an obstacle to work with. If you have that, you stay behind it when you see their big ol' batwings in front of them. Then when it is down you run up and knock them out of cover and pummel em. From range; you can use instant shots and pick them to death while LOS-humping.
Now in a crowded team fight a sniper can get you pretty good and you may not have the luxury of LOS
Luxury of LOS? What about luxury of time? I can't really imagine a circumstance in which you can afford to just hide out of LOS for twenty seconds in a warzone.
Then I was going to explain about how OS makes this tactic not work, but I realized you said "even in sub-50" and realized it was not really applicable.
I may be a little overly dependent on OS in duels, but it's SO cuddly and so wonderful to force melee to fight in.
Snipers do pretty well in duels. Except against Concealment Operatives, who CLEARLY need to be nerfed some more, and to a lesser degree assassins/shadows.