Katyusha is well-balanced imo. it is deadly but allows players to react and run away after the first volley. panzerwerfer on the other hand, is kinda op.
ML-20 is a good unit, but the presence of CAS negates the use of it. It is kinda sad really. CAS + Jagdtiger/ELefant is such a deadly cobination
Something new needs to be done to the Special Rifle Command. SNipers are useful, but the scout car aint that special. Penals are okay imo, but there are better options like Shocks and Guards
don't counter the mortar pit with mortars. It takes way too long, especially if the mortar unit is braced. Best bet as Ostheer, is to get the mortar halftrack. Use the flame round ability to deal massive damage to the mortar pit. As OKW, the Leig can bombard it from long-range, forcing the pit to constantly brace. Volksgrenadier flame nades are also extremely powerful tools. The Walking Stuka does a lot of damage as well, but only use it if there is nothing better to shoot at.