@LS5_71 The problem isn't the helicopters per say. Honestly when it comes to balance they could use some reduction to their durability but outside of that id say they are in a good place.
The problem in my opinion is twofold. How many choppers are available on the map, and the available counters to them. Right now we have a major imbalance in vehicle spawn tokens. You have the Attack group (Attack Helicopter / Jets) and the Transport group (Nightbird/ Transport vics). This is where the hiccup starts.
The Nightbird is not a transport vehicle, it is an attack chopper and should be categorized as such. Players should have to pick between the either using the apache or the nightbird. By doing this, you would reduce the number of choppers on the map which would be less oppressive to the infantry.
Example:
In a bot match on the Hourglass I have 3 tokens for Air. 2 for attack and 1 for transport. This means I can have 3 choppers in the sky which is maximum anti-infantry. If we changed the token system to "jets" "helicopters" and "transport". Then put nightbird and attack helicopters in one section and disperse the tokens. Then we have 1 jet, 1 chopper, and 1 Transport. So basically one chopper either nightbird or attack heli would be on the map at any given time. This is much more manageable for the infantry.
The final issue is the lack of available counters to the choppers. Their Anti Air missiles makes them a threat to jet fighters (there natural counter) who cannot engage choppers enough. The fact is a chopper can "skybox" by raising to high altitude and force jets to engage them from below (which is usually suicide).
As for the stinger missiles the infantry has. I feel like they should deal significant damage to nightbirds, apache's, and jets. Given how hard it is to lock and attack them. I rarely get locked by infantry as a jet, but when I do I can flare it. On the even rarer occasions where I do get hit. It should hurt me bad.
I get your frustrations though, I primarily pilot a jet so I target choppers so they are not harassing ground troops.