let me guess,
1. u are new player that have no idea how to deal with the most weakest helis in battlefield game.
2. the choper pilot / gunner are level 200++ with tons experience
3. the map is manhatan bridge, there is no way that player got 100+ player kills in other map, or its bot lobby.
4. Vehicle in bf6 are the most weakest in bf franchise, specially aircraft, any aircraft.
5. Where is rpg, tows, mbts guided ammo? shot them with those things . no need huge skill or effort, spam them.
conclusion : probabbly team diff or skill issues. you go try fly hellis for atleast 10game, any maps, conquest or escalation or what ever. Then u will going to understand how awful helis in bf6 actualy are.