There are spam, blobs and deathballs.
The problem is the burst and long range damage some of this units can deal out and the lack of penalty since they can retreat to forward points most of the time.
Demos, 120mm mortar, 152 Howitzer, Scott, Priest, Sherman HE shells, T34 crush, ISU HE Shells, KV-8, Katyusha, various call ins, IS2, cheap and plentiful flamethrowers, B4
Demos, 120mm, Scotts, Sherman HE, any medium tank crush, ISU, IS2 and so on are way too good on countering single squads but not effective against "blobs" (deathballs are easy).
Mobile and static artillery are the only real blob deterrents.
While i don't want the ol KV8, i fear more a Sherman with HE than this pitty thing. Gone are his old days of glory.
Flamers are not good against blobs, since the splash damage is almost negligible.