Slitherine

The German copy of the 82cm Soviet Katuysha rocket launchers, the Raketen-Vielfachwerfer had racks of 48 rockets. Anyone have an estimate of what this weapon system's damage stat would be? The german copies added spin stabilization to the rockets, which made them more accurate.

If they are firing soviet rockets or direct copies you could base the effects on the nearest equivalent soviet unit.
If the number of rockets fired per salvo was a lot different from the equivalent soviet launcher, you could adjust ammo count, RoF or damage until you get something that feels about right but isn't overpowered.

Unguided rockets are notoriously inaccurate,so better accuracy might not make a lot of difference in Panzer Corps terms - missing by 200m is probably not much more effective than missing by 400m. However, I'm not a rocket scientist and could be missing something important.