The problem with 300 ping players is that the ranged aim intended for 50-80 ping players will cause projectiles to pass right through them without hitting them. The reason is that you only need to lead a normal ping player by 1/20th-1/10th of a second at most, while high ping players you have to lead by 1/4-1/2 a second, which is a distinct and noticeable adjustment that you have to make during a battle situation.
That's why you do better when you have the high ping. On your server you are getting hit by ranged as you should. On a server where you have a high ping, they are shooting where it shows you to be, but due to lag, you aren't there.