isu-122 = jt (profit)
and is-2 rebalance = KT
panters / tigers = is-1/su-100/kv-85
Funny how the Russian guy wants realism...
So... ISU-152, IS-2 etc. had HORRIBLE reload times. Their optics weren´t on par with German optics. Their ergonomics were poor. The rounds carried were half as much as those of regular tanks. IS-2 had to set the gun to standard position after every shot in order to reload, having to readjust on target after every shot, leading to poor target tracking.
Panthers and Tigers were much better than the IS-1 and KV-85. The IS-1 flopped and barely saw any action. Hell, the KV-85 has the 85mm of the T-34/85 which was insufficient to penetrate the Panther frontally.
The IS-2 is hardly comparable to the KT as you claim. KT is a different league, in the same weight category the Panther is more comparable. And the Panther was the better performing machine, having the flatter trajectory, reload time (3x as fast), optics, crew comfort etc.
In general Soviet tanks were CLUMSY machines. Looking good on paper because of a big gun but lacking in everything else.
If you wanted realism, your Soviet tanks would be pretty much weaker than now. There would be more, but complaining that they are too weak on a 1v1 basis is wrong.
On topic: That being said, the ISU-152 and JT should rather get a reload time increase and a minimum range of 10m. I think that will be sufficient.