Countering IS 2:
Have 2 panthers. Have them both attack since it CANNOT go on a tank killing spree, something that the King Tiger can do. Have a King Tiger, Jagdtiger, or Tiger to single handedly kill an IS 2. If you pick defensive doctrine, 2 panthers are the best option in my opinion.
As Panzer Elite, use Light At Halftrack to break its treads, then send in infantry and put Marder IIIs at a range beyond the IS 2s sight. Or Use AT Halftrack to break treads, then use Henschel. Or use Jagdpanther if you want to single handedly take on it. Or just use multiple Panzerschreck squads.
About the topic, even though I would prefer Panzer IV over Panzer III, I did come to accept why the Panzer IV is not being in the Ostheer.
