Alright, so after extensive testing I found that AI actually can see the targets, reports them, orders the second pilot (the gunner) to engage BUT nothing really happens, they simply fly towards their targets and keep flying above them until they got shot down by enemy fire. The interesting bit is that if I switch all on-board weapons to the pilot (not gunner) in pylon settings they'd at least begin to use their cannon but that's it. I also can see that the target is actually being selected as the square on pilot's HUD is put around it (in Ka52 for example it means that the target is actually being pointed by gunner's laser targeting system). So they def see the target and can shoot, except they just don't until it's 2-3km close.
It's also worth mentioning that if the chopper have fire-and-forget weapons such as AGM-114L they seem to use them at proper distances like 7-8km.
So, it's obvious that something is broken here with the heli AI, and the question stands where should I seek in game archives for the actual heli AI scripts. I'd greatly appreciate if someone would point me in the right direction.