After some consulting and testing I would dare to say the design is wrong to force too many helicopters that are not in one group (therefore not coordinating their paths) into a small area moreover with some challenging LZs.
In a warzone similar situation might have lead to an accident, a collision as well. Allowing such uncoordinated dense traffic would be rather a HQ-failure. The helicopters indeed do crash into each other or the environment, but only if they are forced to do avoid several another collisions at one moment. That's why irl there's always a human pilot, AI can never beat the human improvisation :) And even though the accidents are still the major cause of death and injuries in today's warzones.
About the directions and pinpoint desing. Generally said it is best to leave the AI some freedom. Especially extensive scripting and making the AI to perform a simple action in an precisely delineated way can have a much worse result than giving the AI sort of military-fashioned, simple orders, and leave it to chose its own way to deal with it. In my opinion a mission designer in ARMA is rather a commander (with all the risks such person has to keep in mind) than a movie director.
I'm sorry for atm I can't assist you with the mission design itself, please don't hesitate to use our forums in that regard.
To be able to investigate wrong AI behaviour, I need a very simple repro, e.g. 3 AIs max.
Ja dekuju :)