Teller mines, TWP on PaKs, even on StuG-G and no, IS-2 doesn't reliably wipe infantry or PaKs, out of all tanks only T34 is worse against infantry then IS-2.
All factions use different means to fight off heavy armor, 3 of them have 60 range TDs, 3 of them have potent AT guns, 3 of them have handheld AT that works more or less and so on.
Raw firepower isn't the only way to deal with heavies, which every soviet player can tell you from the first day of CoH2 and ost definitely does not lack in variety of non doctrinal options to deal with heavies.
And who talks anything about ost panther?
If anything, OKW one arrives way too fast.
No offence man, but your lack of actual playing time warps your perceptions here again. IS-2 might not reliably oneshot Paks, but it decimates them and all infantry if not with the main gun than with the DSHK. Ostheer, in practical terms, has no truly effective means to deal with ie. an IS-2/ISU outside of its own, doctrinal heavy armour, especially the Elephant. Barring that, the Tiger can function to anchor your Pak line, soak up damage, and kill infantry, but Pak/Tiger on ZiS/IS-2 fights almost always end in the Soviet favour in the long run since they simply have better survivability and better means to kill the opposing AT guns. TWP is a strong ability obviously, but its nowhere near enough to put that fight on an even footing. BTDT and bought the t-shirt too often. The OH Panther, while indeed nondoctrinal, is a noshow in 1v1 anyways.