I can understand the frustration with killing tanks in the game. I am not sure (I am definitely NOT a programer), but GV damage SEEMS to be mostly location specific. I say mostly because sometimes there are those unaccounted for instances when I think I shot the driver's postion and he doesn't die, or I don't hit it and they do the Pop-Tart manuever (you know, where the tank pops up off the ground, hovers, rotates 90 degrees, and then explodes). Most of my experience has been that if you get a penetration hit on the driver's position, the GV is toast on the first shot. Likewise, a penetrating, damaging shot (you can get penetration hit sprites without doing damage) to the turret will render the main gun inoperable, with the same being true for hitting the engine area.
Now I would agree that you should be able to get one-shot kills on tanks without having to shoot the driver specifically, but I assume that this is something that they could not easily or fairly model in the original AH (I can't imagine what it would be like to model spalling without someone claiming foul). Since I cannot speak for AH2, I will say that from my experience in the MA and some of the testing I did for my GV manual, there does seem to be some kind of threshold that, once reached, causes damage and/or destruction to the subsystem or vehicle. In other words, I think that if you do a greater amount of damage to a tank or vehicle, that vehicle will be destroyed, even if you do not get a critical hit on the driver's position. Once again, this is simply conjecture on my part, and not based on any concrete evidence that I can point to.
As for those instances where people have problems killing enemy GVs even when they are shooting the sweet spot: I honestly don't know what to say. I can say that whenever I got shots on the driver's slit or the front part of the tank, near the side (so the shot would penetrate on a line with the driver's position), I would get one-shot kills almost every time. I'm not saying you are mistaken, only that I cannot explain what is happening if you are hitting the driver's position. I will say that it does not surprise me that Panzers are killing Tigers on side shots. In fact, you can get side shot penetrations of Tigers at ~2.2K distance, but it will take you about 5 hits (by parking shots in the same location: turret or driver's position) to get a driver or turret kill, whereas it only takes one well aimed shot at ranges below 1.9K to kill or damage the Tiger.
A final note on damaging ground vehicles: try to keep from hitting the engine unless you absolutely need to. Killing the engine results in smoke that is indistinguishible form the smoke related to destroyed main guns. Go for the turret instead and try to get it to smoke first so you know he's not going to shoot back.
The GV aspect can be frustrating sometimes, but it's also nice to drive around being sneaky.
[I keep forgetting original has only one "r"]
