It is really hard to get a grasp on the true relational value of the tanks in the game. Right now the Tiger II has, by far, the highest K/D ratio of any unit in the game, but how much that is distorted by concrete sitting Tiger IIs is impossible to know. I suspect that the T-34/85 and M4A3(76) ought to be unperked and the perk prices of the Sherman VC reduced.
As it stands now I found trying to learn to tank to be a steeper climb than learning air combat as the units you can use initially are so massively outclassed by the commonly used Panther V G, T-34/85 and M4A3(76). After many deaths I managed to gather 8 perk points by killing a Wirbelwind and a Panther V G in a T-34/76, though the Wirbelwind tracked me so I couldn't retreat to land the kills, the Panther was already turreted when it came out of the woods about 200 yards from my crippled T-34/76, so I put a HVAP round through its side as it drove by, killing it. The thing is, given how long it took me to get those 8 perk points I don't want to risk them by grabbing a T-34/85 or other cheap perk GV given how often I simply died without ever spotting my attacker. I'd want at least 50 perk points to buy many T-34/85s before I start trying to use it.
To that end, I would suggest a few changes to the GV system. 1) To "Land Successfully" you would need to be either inside a GV hangar or have no GV enemy closer than 3000 or 4000 yards and no airplane enemy closer than 2000 yards. 2) A method of determining if you are clear and free of enemies and able to land. Perhaps limit this from being displayed within 5 or 10 minutes of you having fired a gun or had an enemy round/bomb/rocket land within 500 yards of you. I think that these changes would reduce the concrete sitting and allow a much more accurate assessment of the true relative value of the tanks. Perk price adjustments could be made as needed.
Of course I would also limit perks to being used within the arena in which they were earned.