You need to understand that just as Panther is mediocre in AI and pretty good at AT, Pz is good at AT and AI. Su-85 has non existent AI and pretty good at AT, T-34 mediocre AI and AT. Now what I want you to understand from this statement is that all the Axis tanks have both AI and AT whereas Soviet has to field SU-85 specifically which lacks AI. Elefant and ISU fits perfectly in this jigsaw where Elefant has no AI and ISU has pretty good AI and mediocre AT for 260 fuel. I don't want to simplify this anymore.
Also in regards to snare Axis have the best of snares and it is the pivot of their structure whereas Allies suffer from it and have to spend fuel to upgrade for snares.
I know mate, I hope this does not sound arrogant but you are talking to one of the few people in this forums that can claim to have seen literally 90% of vehicle stats and one of the even fewer that regularly uses the stats for calculations. I know how these units work, and I don't agree with all of your unit descriptions.
The point is different though. In the first post I quoted to claimed that the ISU had bad scatter at long range which would make it rather ineffective and unreliable vs both AI and AT. I have provided simulation data that regarding AI this is not the case and that the ISU reliably hits squads for at least 20-40% of health if used correctly. To the AT part I responded that ISU and Elefant have the same (actually they only have a very similar) accuracy profile and the ISU has a better scatter profile. So at least regarding hit chances, the ISU is not worse than the Elefant.
I now know even less than before what your train of thought on this matter initially was.
Its not good to do much to a panther facetanking it from 20 range that's supported by at least 1 PaK.
Source: Did that.
At the very best, ISU AT is supplemental as literally anything above PTRS outperforms it by a long shot.
You can't mention damage and deflection without underlining the fact it has longest reload time in game right next to KV-2.
I don't know why you treat it as a revelation that the best AT brawler in the game combined with the best ATG in the game can actually deal with a hybrid unit at one of its weak spots. I would rather say this is quite expected.
Now more to the point: provide some data on your claims, because my calculations say otherwise.
In your scenario - 20 range, ISU vs Panther - the ISU has the same offensive performance as a SU85 with an expected TTK of 32,8 (ISU) vs 32,9 (SU85) (with very slight estimations regarding pen chances since I don't have the tools with me to make a 100% accurate calculation).
The AT is mediocre for its price, yes, but claiming that "anything above PTRS outperforms it by a long shot" is not a hyperbole, it's almost a lie. You regularly ask people for replays (which is alright) to back up their claims after claiming units were OP or UP. So I ask you now for your calculations on stats.