The other thing that annoys the crap out of me is that you can somehow fire the missile before the lock is done, and when that happens you've wasted it.
I had a game on firestorm where I was shooting at a painted jet, and it managed to flare away the first one (why, it's painted, it should ignore flares!) and then when I locked and fired again it managed to outrun it somehow.
The damage is pitiful as well. It should one-shot any helo. That's the entire point of it being an anti-air weapon. You make yourself completely incapable of defeating vehicles (barring a miracle where someone is regularly painting with a laser des) in exchange for not being able to kill the thing that your entire job is now to kill.