that is what it is meant to do. late game units, progression, positive leveling.
that is the design.
And no, it cant walk in and kill infantry and walk out like you made it sound uncounter-able
Yes It is.
260 armor was bounced a lot AT even from SU-85. This is too hard to counter while brumbar fire 1-2shot kill whole squad.
They do have high HP that already need 5-6 shot form AT to take it down. plus they performance are better than KV2. I've test more than 10 time.
for the same thing on allies side
ISU-152 Got nerf too. both armor and range.