However, I must agree with OP on this one. What you are describing is all good and well in theory, but as OP said its hard to destroy lets say Piv with Assault gun, or AT gun for that matter in the hands of a unskilled player. Why, well all he needs to do is click near tank destroyer or at gun, get little bit lucky with line of sight and it negates skill. Its difficult to manouver fixed gun vehicles to fight of noob. Even if the tank is seen from far away. You couldn't accidentally flank Marder in the hands of skilled player.
As MagpiesFlight said somewhere: "it takes enormous effort to defeat spamming noob" Because infantry isn't punished in the hands of unskilled player enough. Basically, he can cross roads, stand in open and come up close to infantry in cover with minimal loses.
I wont go into MG in the house supported by mortar, being a lot more viable option than using snipers, micro-ing your way to the house to drop molotov or nade that has very little effect.
It is far, far harder to flank an SU-85 with a P-IV than to beat a P-IV with an SU-85 right now. Even with the cone vision and AT-nade changes. An SU-85 with a spotter can reliably mangle two unvetted P-IVs. AT guns are a bit lackluster at the moment but supported properly and overlapping each other they do alright.
I agree with the bit about infantry and especially MGs in houses.