Attack Helicopters are a lot of fun. I had the same sort of thing happen the other day, but I was the gunner. This guy was a great pilot, he'd do all the maneuvers that I would've done in the situation, like you said, flying low at high speeds to avoid lock on's, we also defended the enemies helicopter until our team stole it. But yeah, the soldiers are very irritating, all you need to do is look at as much of the map as you can while they're locking on, then when they fire, trace the missile and light that area up.
Scout Helicopters can be a little more difficult depending on the other team. Only because the most likely place to get one is on the Canals map, where the enemy has a buttload of tanks, and it's really not too difficult to bring down a helicopter that's flying low with the main gun of a tank. I mean, I bought a jet down with one, and they fly around all crazy like.
Also, I swear so many people had started to use the AS VAL, I noticed it just as I got to around level 44 and then to 45. Didn't both using it because I hated it in the Comrades mission.