Dont zerg. Leave the zerg and run by yourself or in a small group. You'll realy improve however you will get killed a lot by a zerg of players who dont want to improve but just want to RD spam or snipe from behind a massive zerg.
However while you become better and better from not zerging and learning your class and character better they wont get any better because they need the zerg. When you manage to find one or a few dedicated zergers by themself you can get that 1vx against them.
Also play a stam nb... helps a lot if you want to sbe that mlg pro player with all those 1vx moments.