Baloney. The Halo 3 Warthog chaingun was absurdly powerful, had no overheat mechanic, and was only really balanced out by the equally absurd number of EMP capabilities on those maps and the ridiculous prevalence of the awful Spartan Laser - not like those helped when you spawned in the middle of nowhere (hi, Standoff. Hi, Rat's Nest). That was also the game that reintroduced the Banshee bomb in multiplayer, one of history's great mistakes. Even the Ghost cannons, on a vehicle that should have been 90% about map traversal, killed extremely quickly with very little effort. Even everyone's beloved Chopper had insane physics impulses on each rapid-fire shot, so good luck recovering from that if you're on a flag run in another vehicle. Vehicles, apart from the Banshee, haven't really gotten any more powerful since then. If anything, they're easier to deal with since you've got the ability to damage them at spawn.
That's not to say I think the persistent vehicle damage is a good change, but I'm firmly in the camp that thinks that vehicles should be first and foremost defined by their mobility advantages, not as tools of Hold RT For Mass Destruction. They function so much better when they are, tanks aside, used more for objective runs and for in-and-out harassment. Not that they've ever purely been about that, but I think their role in combat really needs to be rethought to force people to use them with more care.
Standoff came with a Plasma Pistol, Plasma Grenades and a Power Drain in the base as well as Rockets and Plasma Grenades at Camo. Not ideal if you're spawning outside the base on the right side (when looking to enemy base from your own.) Even then a decent driver would avoid that back road like the plague due to the exits of the base making for an easy ambush. Hogs died very easy if the driver wasn't a great driver on Standoff.
Rats Nest is a similar story. The inside bases are littered with weapons that can take out, or at least screw with a Hog. Plasma grenades, PP and Brute Shot are easy to grab, free of Hog hassle and with some risk a Trip Mine is available to you. The only time a Hog truly takes on Rats Nest with ease is when a team is spawn trapping you. The Hog on Rats Nest is a near non issue outside of Team of 8 vs Randoms unless the teams are greatly unbalanced. Even a good driver finds Rats Nest hard to drive on due to its corridors, corners and single driving route which make for easy ambushes.
The Ghost cannons are powerful and do need toning down, but not to Avalanche Hornet levels. It should be an in and out type of vehicle. It shouldn't be around for long in an area or the driver should expect to be punished for it. I don't think it should be nearly entirely about using the thing to get from A to B faster though, that basically makes it redundant, and we already have the Mongoose to fill that role.
The Hog is a strange one. I agree with the overheat mechanic as it makes a gunner think more about what he's shooting at and if the shots are worth firing. It also makes the Hog more of an in and out vehicle as the Gunner can't pepper everything in site and they have to back off as they can't defend themselves momentarily. I don't think it should be easy to kill like it currently is in Halo 4, and was in Reach.
The Chopper was a beast and I'm never going to deny that it practically ruled the roost if it was on the map against other vehicles. I don't feel as though it was hard to take out though. The exposed driver, and the physics the vehicle itself had made it a less than difficult task. A BR from the side at the back would send it into a spin. So would a grenade.
Also the scenario you gave is a strange one. Surely if you pulled flag and wanted a simple escape you'd have taken out the Chopper first. The Chopper is a threat and should be treated as such in those circumstances. That's just poor teamwork.
That's one of my issues with Halo 4. The vehicles haven't really become more powerful, yet the ability to take them out from spawn has been handed to the players without a thought about what this would do to vehicle combat and BTB as a whole. No teamwork, no communication, just destruction. The only way you're getting some work done in a Vehicle in Halo 4 is with a Banshee, or a decently guarded Scorpion.
Both the players ability to take on vehicles from spawn and the vehicles themselves need a lot of work, but I really feel that a good driver, pilot, or gunner should be rewarded for having the skills necessary to remain alive and get kills in one vehicle.
Agreed on the Spartan Laser. It really is awful for vehicle combat. The Banshee bomb is also a problem, and while 3 may have introduced it, it was damn near useless. Pretty sure it took a near direct hit to kill.