I would like to suggest adding Infantry support guns as T2 unit for both factions and buff AT guns accuracy against armor.
Infantry support guns would provide short range direct fire with small High explosive rounds (weak, baby version of ISU 152 rounds or short barrel StuG) and light barrage ability similar to ZiS 3 now (but It could be removed from AT gun, it's ridiculous).
Also they could deal with vehicles using HEAT round shoot ability (pretty much an 6kg AT nade) able to severely damage/destroy light vehicles and slow down heavier ones - it would had chance of damaging engine like AT nades and panzerfausts.
Osther -
7.5 cm leIG 18
Cost 380mp
Crew of 4
Barrage ability - free, 50s cool-down
HEAT round shot - 75 munition, 20s cooldown
Faster rate of fire than soviet counterpart
Soviets -
76mm regimental gun M1943 - it's carriage is same like in small 45mm AT gun from campaign.
Cost 380mp
Crew of 6
Barrage ability - free, 70s cooldown
HEAT round shot - 75 munition, 20s cooldown
Larger damage and AOE than german counterpart