You have to remember that the smoke perk was added to the choppers after many complaints about it being far to easy to down a chopper, once you were locked on with a trace dart you were dead. At least with the smoke you stand a fighting chance (if you have it enabled and are quick enough!). You definately have to work as a team to take them down now which I quite like.
Some tips for budding pilots.
1. RPGs turn slower in the air so it is possible that if you do an emergency landing that the rocket will hit the ground rather than you.
2. CGs turn faster are are more difficult to evade in the air, if you've not got smoke or have used it but they've locked on - your only hope if to get behind a building/wall/tree and cross your fingers (or bail

)
3. AT4s are guided manually by the operator so flying in straight lines will get you killed. You often don't get a warning in the cockpit as well which makes it tricky. Your only hope is really to fly fast and low. If you see a rocket coming kill the operator before inpact and the rocket will splash down somewhere else.
4. Untraced RPGs/CGs - you have no hope really other than to try and keep your flight pattern random in terms of turning circles, height and speed. Try and keep high so it's more difficult for them to blind fire you.