Try my repro-mission. Each from the 8 BLUFOR missile specialists, has a launcher and every has 4 Anti-personnel Missiles but none of them will use it against 8 fighters OPFOR!

Note. BLUFOR located is in a favorable position for firing from Launchers, because the position is high. This squad has a the highest level of AI skills and has DESTROY waypoint, with "Open Fire" mode.
Even only one fighter, from 8-BLUFOR soldiers, could easily be cover with deadly fire enemy OPFOR-squad and easily destroy it, but none from the 8 AI-units can't do this! For example, if we will change the players team and place the player in the BLUFOR-squad, then the player is alone and by means AP-missiles can easily destroy the all OPFOR squad. But AI not able do it. Instead the defeat of the red squad, blue team dies. OPFOR is easy to destroy them. This is nonsense.

Some prerequisites in order for the AI can use AP-Missiles:

If the AI is watching the crowd of enemy soldiers.
If the enemy soldiers located is in cover or buildings.
If a Missile specialist located in an advantageous position, for example high over the target.
If a Missile specialist has hight levels of AI skills, then he should use it at big distances. (1-1.5 km)