I'm not as highly-ranked as you, but from my experience I'd say Jagdpanzer. kites well and gets a nice HP buff at vet 2. Command panther is nice too, spotting for itself + mark target makes it much more effective than standard panther.
My issue with the Jagdp4 is that it fails to penetrate the frontal armor of the IS-2 far to often to be reliable. This unit
seems like it should be a viable counter, and believe me I've tried, but I always end up feeling underwhelmed when using it. It's DPS is just bad. The raketen is decent if you have the luxury of a building, but out in the open it gets decrewed very easily, and trying to keep a vetted raketen alive versus an IS-2 means that you can really only risk taking a few shots before forcing a retreat.
My biggest issue is finishing the damn thing off. Shrecks, raketen, and the jagd can't chase down a retreating IS-2 which means in the long run your just feeding the beast vet. I find myself needing a strong, mobile anti tank vehicle, and the panther doesn't cut the mustard against the IS-2, which leaves me scratching my head with what to do. I'll give the command panther a shot, but in my experience the added sight range doesn't really help because at max range it still has trouble penetrating. Maybe some of the pros can give some insight into the numbers, or what units are designed to deal with this thing, but I really can't find any reason to believe that its not over the top at the moment.
I want to see a replay of OKW tackling an IS-2 in 1v1. I'm sure it's been done, but I want to see it in the context of an evenly matched, reasonably high level game. Any takers?