It's not RNG. An experienced pilot can easily dodge missiles. Sure, you can't always dodge due to circumstances such as being too close or flying too slow, but it's not RNG.
I've heard the cries of many frustrated pilots claiming shit like this. Typically, the infantry with the AA launcher waited for the perfect moment to fire the missile, therefor making it impossile to dodge. But, again, this is not RNG.
Now, there is a difference if you're in a lower grade helicopter (such as an AH-9) where there is not an actual radar. For the most part, if you can't see the missile, you just have to use your judgement and dodge when you think the moment is right.
In a vehicle such as a jet, Ghosthawk, or AH-99 Blackfoot where you have an actual radar, wait for the "M" of the missile to reach the edge of the inner-circle. As soon as it hits that inner-circle, pop flares and make a sharp turn. Pitch slightly downwards if there's altitude to spare, so you can get more speed to get away from the AA before more missiles come after you.
Using this method, I've achieved a personal record of 7 dodges in a row with a Ghosthawk, having the 8th disable me after I lost too much speed after a dive.
Hope this helps any new pilots out there. Good luck!