Vehicles are a big threat.
Jets are still raping on some maps i.e. paracel storm, shame, they really need to do something with regards to jets, pointless playing when you got a good jet pilot i.e. paracel storm the other day, couldn't use any vehicle without dying 5-10 seconds later, even the gunship was taken down as soon as it spawned, as soon as I see/encounter some pro jet pilot, I leave, no point, **** all you can do against them.
Boats need to be reworked imo, have a similar setup to attack helis (always cautious of using tv missiles as you can't do anything until the tv missile has impacted something or gone out of range, so you're extremely vulnerable during that time). The only thing that needs to be nerfed with the boat is the splash damage of the 30mm rounds, they are easy to take down if you have a few engineer guys on them and against good jet/heli pilots, you don't stand a chance, you got no cover, only time is when the storm kicks in and if someone gets a critical hit on you, you're a sitting duck, so easy to TV missile a boat. I think the mini gunners should have some shield or cover too as they are easy targets especially when you can't move the boat to protect them during a tv missile. I am using the burst cannon as it is much better for dealing with the aircraft and boats etc. at range and TV missile for boats, helis, jets etc. too. Gunship can take the boat out with ease too, you can TV missile it (done it a few times) but have noticed on some maps that once you get to a certain height you can no longer control it so have to just have to use it as if it where a RPG/SMAW or just stay on the other side of the gunship so they can't do anything

(that is why I tell people to spot the gunship, makes it easier to avoid via using the mini map)
Tanks are beastly but can still be taken out easily with a few organised engineers/tanks and not to mention aircraft can still rape tanks, thankfully not as much of a problem since there is more cover from aircraft in most of the maps. HMG/LMG rapes the infantry, sabot shell is great for taking aircraft out but I use HE shell as I encounter tanks more often so need the extra damage + you get used to the drop/speed.
Attack Helis are powerful too but have probably had the biggest nerf from bf 3 to bf 4, go through the ammo very quickly and it takes forever to reload, cannon has very little splash damage and does nowhere as much damage to vehicles, where as the rocket pods do more damage to vehicles but not as much to infantry.
A good scout heli can rape with those explosive rounds and even more annoying is when someone is just constantly repairing him, pretty much nothing you can do unless you have 3 or so guys firing stingers/SRAW/RPGs at him i.e. on xfactors squad up video the other day, the scout heli was raping his team and even when they had 3-4 guys with stingers etc. they couldn't take him down. I can fly helis well enough and avoid lock ons etc. but my aim isn't precise enough to take infantry out
Remember this game is all about the angles, front is the strongest followed by the sides and then the back. The main tank driver can't shoot any infantry that are behind them on the same ground level. There is also more to it than just front, side, back, xfactor explains it best:
My main tip for vehicles is to use the 3rd person view when driving around/looking for people, especially when tanking, easier to see/spot, can see more, hear better etc. One thing that I like doing a lot lately is if I am against another tank and know that I won't win, drive right up, ram him and then jump out and get that straight on rear shot!
For boating, use the full map, either press m or have it on a second monitor and keep an eye out for enemy boats + keep an eye on their spawn every couple of minutes as you are getting tons of people just TV missiling from their base now and the problem is, the auto AA will shoot your TV missile, which makes your aim go all wobbly.