A mistake with your panther?
Blitkrieg/Smoke/heavy armor... Well don't panic...
A mistake with your SU-85/ T34-76 or IS-2(!)... Not sure you will keep it alive.
While smoke is doctrinal, blitz only works without damaged engine, what should be first thing you aim for as soviet fighting a panther. if engine is crippled, even heavy armor does not help too much, as su-85s or zis can just fire at it withput fear of getting circled
and by the way, su-85 and zis get tracking to hunt down damaged panthers, just use your abilities right, then nothing is invulnerable...