Thats sorta my point with the 'lack of offensive action stats' thing. Really, the only way to ensure they aren't camping the spawn or concrete camping is if they're attacking, so we would want to use the 'killed on enemy territory' numbers if such stats were available.
I guarantee you the vast majority of Tiger II's killed by GV's are killed while in a TT fight, or at a busy spawn fight, not while they're being used as anchors for a defense line, or concrete camping, or even when they're attacking. In all those instances, the Tiger II is (or should be) part of a coordinated group that would make flanking it out (the only way to do it) much more difficult.
But regardless, our GV's shouldn't be physicly incapable of making an attack on an enemy base without 6 wirbles for every 1 tank of theirs (even then the wirbs don't even stand a good chance at preventing someone from bombing, let alone forcibly stoping a bomb attack. All they do is stop straffers and make the bombers think twice).
Thats my point with the need for better AA (as of the most recent patch at any rate, we'll still have to see how the new view ranges affect things). For GV's to have potential as offensive weapons without the need for the field to be incapable of even trying to stop them, we need something like a spawnable, player controlled FlaK 36. It wouldn't even be all that unbalancing, since it will (or should) be easily killed by even a D3A, difficult to hit a manuvering target. Also, no proxy shells, you'll have to set the range by hand.