When thinking about unit balance you should think about the faction as a whole instead of comparing it to other similar units. OKW has excellent support with shrek'd volks, lmg obers, the recent raketen, jp4, etc. soviets on the other hand have to rely on zis guns shocks and the su85 to help support the is2. They don't even have a mirror to the shrek, and zis guns can be quickly cleared by obers.
The KT shouldn't be a unit that wins the tame on its own, but rather helps to win the game with the rest of the army.
I agree with your post, but the KT's issue is that getting it almost always prevents you from having all those things like the JPIV to support it. The KT by no margin is a bad tank now or useless, but it's roll has definitely changed with the double whammy of the Jackson buff and the armor nerf.
The KT seems to just be in roll a "last ditch" tank in some scenarios were it's you last hope of holding back the tide or turning the game around, or it's just a "seal the deal" tank were you were already winning by a large margin and the KT is just there to end it sooner. The lack of in between is kind of disappointing.
The IS2 is great because it is much more easy to acquire and pump out in numbers than a KT, and normally you won't even see it alongside SU-85's because teching doesn't have much a point when aiming for call in's.
TLDR: call in meta is dumb, why hasn't it been fixed yet.