The guided shell needed SOME sort of nerf--it is the most effective AA in the game and there is no real way (ECM jammer lol) to stop it. I would have rather they add a laser beam, similar to the SOFLAM, to the tank that's locking on, along with a lockon signal that differentiates between AA rocket launchers and laser guided. We'll see how it plays out, though...enjoy your super guided shells while you can!
Not sure how I feel about the stinger buff--I personally thought the stinger was pretty effective. If you are against a pilot with flares, you can get a hit while they reload. If there is a gunner with flares, it's rightfully not so easy.
Generally, I like the balance in the game as far as infantry goes, but the air/AA still needs some work.