This kind of misses the point of the thread. "Without Panzerschrecks they have no use" is the essence of this topic. You say they have use because they have Panzerschrecks. I don´t deny that. But that´s pretty much the only thing they are good for. And that is the point.
Two PG models with StG44s won´t be deadly at all. I´m not suggesting to make them snipers, but the drop off of the StG44 should be reduced. So they are still on par with Kar98k damage on long range.
The funny thing is that a Pak + Gren wall is still more cost efficient at taking out tanks than any combination of PGs.
I´m sorry but as a pretty high leveled Ostheer player I can tell you if I want to win a game, I´m not building PGs. And I never ever build them for their AI value.
Your pak + gren wall is situational. You must know where they're coming from and LoS. Let's just say 1 pak + 2 grens, 240x2 + 320 vs 2 panzergrens, 340x2. Here comes 1 sherman tank with HE round. If he comes forward in, you can get off an AT shot and then a snare. Okay it wins. If it flanks... well 1st faust won't snare it. I'm not sure if second one is. However, smoke the AT gun, kill the infantry or smoke the infantry and kill the AT gun. 2 panzergrens can just shoot it on site at any direction reduce HP to instant say 30% HP if not 0. If they are smoke prior, they can just walk out and continue to shoot and not have to set up like an AT gun would.
Panzergrenadiers are more versatile and both strategies work better in different scenarios. Thus, they are separate units with slightly different usage. Why is volks blob preferred instead of rakuten blob? well, it is more versatile. It can deal with infantry alright and shoot at vehicles as well.
Like I said, buff panzergrenadiers all you want if you want them to be AI specific. Buffing them along with panzershrek will spell another blob. If you want to keep AT option, with unit buff, i'd nerf that shrek to a panzerbusche like the ones you see in ToW. (similar to AT rifle)