Should have expected as much, but one of the custom classes has an AT-4 as a secondary weapon (bling). Should help a bit against the choppers. I downed one with one rocket, and a UMP clip. You also get point rewards for shooting down choppers and UAVs, so there's some incentive to actually take them on.
Then again, everything rewards you. Kill someone, get a reward. Get killed, then kill the dude who killed you, and you get rewarded for the kill and for the revenge. Oh, and if you do that with the class mentioned above, you get a Bling reward.