-They are both more expensive to build and to reinforce
-You are losing more AI by having 2 zooks than only 1 shreck
-Lower damage and lower penetration against higher armored tanks
-Burst damage. While zooks have higher RoF, what it matters is only the first or second salvo.
People don't care about zook rifles as it's way more scary double bar/1919 rifles.
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.