To address point 1 -4 you are incorrect. you need far less rifles squads achieve the same effects of the a vg with shreks. 2 rifles with zooks will kill a medium tank in the second volley. you will need 3 vg's for the same effect. they win in burst because a riflesquad will do 160 compared to the volks 120 damage . Because you need less squad you are using far less mp.
Your correct on lower AI but i do not judge dedicated AT units on the performance of their AI.
You are also incorrect about the heavies. the zooks do their damage against them through deflection damage. zooks are more less equal in shreks in that department. But BOTH weapons suck against heavies anyway
In short you have rifles who have 24 dps against tanks compared to the vg's 14 dps. also veterancy means that they will receive -50% received accuracy compared to the volks only get 20%. All in all current rifles with zook are significant more potent then prenerfed volks.
so their is no need to nerf volks or to change it.
First of all, i'm just gonna say that whatever they do with Volks is gonna be a mess as at the moment, they are practically a needed evil.
Cost opportunity: you don't lose "anything" by upgrading Volks. There's no good reason to not have the upgrade. If you upgrade 2 Rifles with Zooks, this means you have at most 1 or 2 squads more of Rifles to do the heavy lifting on the AI.
Zooks don't have guaranteed penetration against normal mediums.
Penetration on average:
Ostwind (100%) Stug (85%) PIV (67%) JPIV (52%) PIV OKW (51%) Hetzer (67%)
PV (38%) SPIV (46%) ST (55%)
PVI (40%) Ele (30%) KT (32%) JT (23%)
T3476 Su85 M4C M4 M36 M10 Centaur Cromwell Firefly (100%)
T3485 (100%) KV8 (71%) KV1 (63%) E8 (79%) Bulldozer (85%) Pershing (57%) Comet (59%)
IS2 (45%) ISU (55%) KV2 (57%) Churchill (71%)
Deflection damage is for both at 25% (20/30 respectively). Both "sucks" against them, but they are not meant to kill them rather than support in damage.
Receive accuracy only matters against the tanks MGs, as it mostly have no effect against the main gun of the tanks (with the exception against Flak HT, P2, Centaur)
I don't want this to keep derailing but you asked:
"Can somebody explain to me why volks are an issue but dual zook rifles are not. these guys are even worse then the vanilla vg's"
It's simple. While we can discuss performance of Shcreck vs Zook and Rifle vs Volks all day, the reality shows that we don't see Rifle Zook blobs running around as much Volks blobs with shcrecks. The later is mostly as that it's only and main role.