This is not a case of cheating.
This is a very typical case of a perfect storm of conditions that are in favor of the attack helicopter.
The Map has a lot of cover for the helicopters to hide in
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The gunner seat can perform just fine while the heli remains in a safe proximity to skyscraper cover.
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There are no jets to hunt fliers
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The gunner seat has a very strong toolkit:
1) A cannon that can do great damage to both armor and flesh
2) An AGM that can allegedly lock on up to 800m away and hit even vehicles in the enemy spawn
3) An "aim assist" that keeps the crosshairs where you were pointing them regardless of where the pilot tries to go.
4) Thermal vision that lights up all the soldiers, vehicles and aim guided missiles.
Easy fix:
Get the attack heli the hell off Vegas.
It is just a Great White Shark inside fish tank full of mackrells in here
No balance changes needed.