The biggest issue with the Panther is that it usually offers less dps than a Panzer IV. And even the Panzer IV is arguably underperforming.
In a perfect scenario with which I mean every shot hits and every shot penetrates, the Panzer IV is simply superior:
Panzer IV: http://www.coh2-stats.com/ballistic_weapons/panzer_4_75mm_mp
Reload: 5,3s - 5,7s
Damage: 160
Range: 40
Penetration: 120.0/110.0/100.0
Panther: http://www.coh2-stats.com/ballistic_weapons/panther_75mm_mp
Reload: 5,8s - 6,7s
Damage: 160
Range: 50
Penentration: 260.0 / 240.0 / 220.0
Aim time and cooldown are the same.
The Panzer IV has a way better anti infantry performance added to that, making it even more superior. The Panther suffers from being only good in theory. I would estimate that the majority of tanks fielded in games are Cromwells, T-34s and Shermans. All these units can be penetrated sufficiently by the Panzer IV with higher dps. In my experience the penetration bonus of the Panther is offset by the higer reload of the Panzer IV. Any infantry threat can be countered better by the Panzer IV. And the Panzer IV is already lackluster.
So in my opinion there are three possible solutions:
1) Buff the Panthers AI (making it more multi purpose, which I don´t like since Panzer IV and Tiger fill that role already)
2) Reduce the reload time to match that of the Panzer IV
3) Increase damage to 200 or 240.