No matter what class you are (except gunner) if you aren't level 60 yet you're going to be pretty underpowered in Corsair's. Zerkers can still drop a heavy hammer on people, but without lvl65 crystals and all of your skills you're gimped. You can try to 1v1 people, and you might catch a sucker or another level 40 player, but for the most part you're going to get beat up real good.

What you CAN do, if you are interested in winning and not just having a pvp skirmish, is focus on the objectives. On defense this means using tanks and cannons to shoot the enemy team as they try to knock down your outer gate, and then using tanks and cannons to shoot them as they approach mid. You can also guard inner ladders, which is boring but if you do your job you help ensure the win. Queue up some YouTube videos for your 2nd monitor. What you can also do is pick up bombs, and blow people up who are trying to knock down gates etc., ideally you do this in pairs (bombs do ~75% of someones HP, so you need 2 bombers to get insta-kills).

On offense this means moving the tanks in place to block the shots coming from the cannons on the outer walls, it means trying to ninja their tanks and move them out of place, or blowing up their wall cannons. You can also be a pest to the defensive people trying to steal your outer pyre, since you can't do as much damage to the gate as other people.

Ultimately, pre-65 you're gonna get your butt kicked in CS. Berserker's are also a difficult difficult class, and they aren't the best in large fights, so even at 65 it's not gonna be easy. Stick to the objectives and the things that are not effected by your gear and you can still be a big help to your team.