Since T-34/85s hit the filed later than a PZIV, and even a Panther can sometimes show up earlier than a T-34/85. I think it's necessary to do a T-34/85 vs. Panther series.
Panther cost (600MP/130FU)
Armor 270(F), 960HP, 160damge/hit, 170 penetration
Reload+Aim=6.45+0.125=6.575sec
Scatter 6.0 AOE 0.5
speed max:5.5
Have a Turret Machine gun upgrade for AA purpose and bonus to AI
T-34/85 cost (360MP/130FU but you must pay 720/260 for call-in)
Armor 124(F), 800HP, 160damage/hit, 110 penetration
Reload+Aim=8.45+0.125=8.575sec
Scatter 2.6, AOE 2.5
speed max: 5.3
Panther penetrating T-34/85: 124/170=100%
T-34/85 penetrating Panther: 110/270=40.7407%
Panther finishing off a T-34/85: (800/160)*6.575/(100%)=32.875sec
T-34/85 finishing off a Panther: (960/160)*8.575/(40.7407)=126.286sec (BOOM!)
Though T-34/85 have better AI at main gun, but the turret machine gun of a Panther can compensate this disadvantage a little bit, and notice that Panther is slightly fast than T-34/85. And, T-34/85 hits the field can be as late as a Panther or even later than a Panther.
FULL-RETARDED vehicle balancing.
You can't really ignore the fact that call-in tanks have zero tech requirement. If the panther was a call-in tank at 5cp for the same cost, that would be just ridiculously OP since teching to T4 is prohibitively expensive normally.
That said, I would agree with a small buff to the T34-85, probably increase its penetration to 130 from 110 or increase its ROF.