It'd be a wall of text but believe me, they are completely ****** in BF4 and pose no threat on any maps except Shanghai and occasionally Dawnbreaker. Although on DB the jets / roof wookies can easily negate the heli. I agree that BF3 heli's were OP, but BF4 they have been nerfed so badly you'd be an idiot to fly one without cover.
As a chopper pilot there in nothing you can do on Lancang Dam. Their AA can shoot you from base (and up to 3000mtrs with Active radar missiles) so before you can get into range of the AA you are already disabled and about to die. Not that getting in range really helps.
Base camping choppers...what else would you have them do, flares take 30 secs to reload and everything on the battlefield can kill you. With the state of flares atm you need 1 infantry on the enemy team who knows how to use a stinger (they got buffed today too / you can fire 2 at the same time) and it's a OHK everytime with no defense. Against jets the TV doesn't OHK and as long as they are above 300mtrs in height (heli ceiling) the heli is dead, simple as.