Cheese news: the fact that you couldn't kill the AT gun is because you are aiming at either the middle or one of the models in specific. And the Rifle nade having a smaller lethal radius.
Even when the cover shield appear, i could 100% kill AT guns with Rifle grenades, by aiming at the model who fires (not the loader).
ATGs do give green cover damage reduction against AOE weapons under certain circumstances. I think it has to do with the direction the grenade is fired from, as normally that influences whether or not damage reduction is applied or not (as green cover damage reduction is directional), combined with the wonky circumstances under which a gun shield seems to give cover or not.
#1 aiming directly for gunner model
#2 firing from the gun's left side results in a lethal hit
#3 firing from the gun's right side results in a non lethal hit
So in any case, my claim was that
gunshields […] do generally provide the -50% green cover damage reduction against explosions.
and that is proven true (though perhaps
generally is a bit of an overstatement, as I haven't tested every single angle, but they at least
sometimes provide green cover bonuses) based on these tests (-78hp health damage to the squad while hitting at least two models must mean the grenade did
-50% damage).
Furthermore, I said:
And the Raketen does neither of those things.
Which is proven by replicating the exact same tests with the Raketen, in which no matter the direction it was fired from, the grenade scored a lethal hit on both gunner models:
So back to my original point, regular anti-tank guns do seem to offer the crew at least
some protection against various enemy weapons even though the results vary wildly, but the Raketen
never seems to provide any protection under any circumstances. So personally, based on these test results, I think it's fair that the Raketen can have a 5th crewman - partly - to compensate for the lack of a gunshield.