Well apparently the heavy cover on the AT guns doesn't work/is super inconsistent. So I assume that's not a possible avenue for the raketen.
In game, i would say it only works in like 10% of the cases. What's more effective in the case of the normal AT guns, is that they have a bigger hitbox which would lead to blocking "physical shots".
I just tested in case it was fixed but nope. Each AT gun bugs differently (lol), but for example:
Zis: the shield disappears when looking to the right. You still have a shield when looking in the middle but it doesn't do anything. But when shooting on the boarder of the left side AND been attacked from that side, you would actually benefit from it.
If someone want to further test, just use cheatcommands (first version is easier) with damage UI kickers enabled. Then just use a single high accuracy unit such as an Ober model with vet and check when the unit is dealing 8 or 16 damage. Or faster, just use any unit with nades and see how you are still wiping 2 model AT guns from the front.