The panther right now is super worthless indeed .... for the price of the teching up + heavy panzer company + a single panther, I could have brought out 2 panzer IV's which would do a way better job against the su85.
Panther is USELESS against any infantry (on par with german scout car) and just average as an anti tank unit. What incentive is there to even build the panther now ?
My suggestion is to buff the Panthers range to 60 to equal the su85 and make its main gun a bit stronger against infantry. This would solve all the problems with su85's while still maintaing balance (of course with a slight reduction of su85 reverse speed to encourage flanking)
SU-85 shells have the possibility of bouncing off a Panther's front armor. If the SU-85 is supported by infantry, the Panther is the only German tank that has a chance of destroying the SU, even with a damaged engine.