The reason why helis are so atrocious in this game is not because of their potential to kill, but it create an extremely large area of denial for extended periods of time. Whereas Ins team has no such thing that would come close, either they have long warnings to be avoided, less time and area covered, and drones will only drop one load and buzz off. (furthermore, I'm not sure if it is a bug or intentional, but gunship missiles penetrate buildings quite easily) Not to mention if you are out in the open (especially in maps like crossings) you can easily get obliterated. And worse off, from spawn as well which is mostly open.
This creates an extreme imbalance of fire power that the Ins cannot easily deal with. Sure, you can shoot them down, but it requires specific role with specific equipment armed and ready, which is rarely the case. And even then, the heli covers such a large area which makes them difficult to hit with an RPG (especially the gunship) and not to mention they sometimes seem to dodge them, which happened quite often for me.
And yes, regular gun fire takes them down too, but it takes the entire team emptying all their ammo to get them retreat when they were about to any ways. For context, I had a bipod set up with a PKM, and emptied 2 magazines directly into it, with my team mates helping. It didn't go down, but left after it's timer.
And this is the best case scenario as well. It completely gives an upper hand for a push or a defence or just spawn wipe the entire Ins team when you put it almost anywhere on the map, which the Ins has no such thing that can be comparable.
For this to be resolved, you can add a fire-support anti air system (like Rising Storm 2 SAM) or give a dedicated AA equipment, whether it be a stinger or a Vulcan gun on a techie or stationary. Either that, it can entirely be removed since it just tilts the balance too much towards the security side. I guess it can be nerfed so that it takes time for them to find targets, or they just strafe quickly and leave like the A10 too.
Side note: also, the helicopters seems to be janky, moving rather slow than it should so that RPGs can take them down, which makes RPGs fly in a complete straight path, meaning it is also good for RPG snipe spamming, and not to mention helis are rather glitchy sometimes as well. I like the A10 and the artilleries, but helis just don't seem to fit this game at all in my opinion. At least with the current game modes that we have so far. So unless they specifically add a game mode that is more suitable, or balance things out, I would rather see them gone unfortunately. It is a shame and waste of assets, but gameplay wise, it just doesn't make sense.