You dont need KT to counter IS2.
Panther can do it very well since it has better range.
You can also combine KT with pak 43. KT+pak can easily counter 2 IS2s.
Not to mention that you will get IS2 around 25min while in 4v4 can hit the field around 15. By the time second IS2 arrives you can get a Panther. Even in 1v1 2 IS2s are facing KT and Panther so I have no idea how did you figure out that OKW can get only 1 KT and nothing more.
In fact you dont need anything more. In 1v1 Ive killed many IS2 with pak 43 doctrine (Ostheer one with railway-artillery).
If all things are even, the soviet player will be able to field two IS-2's while the OKW player is still on his first panther and waiting for the KT. Add in the fact volks vaporise trying to kill an IS-2 and the raketenwerfer decrews in like two DShK bursts and you have a very uneven matchup.