The T-34/76 was the best tank in the world, in 1941. It's armour could deflect nearly everything the Germans had en masse. Pak 36, Pak 38, Panzer III 36mm Guns, Panzer III 50mm Guns, Panzer IV 75mm Infantry Support Guns. Only the Pak 40 and Flak 88 could penetrate it at decent range. It could also penetrate the Panzer III and Panzer IV Tanks.
In 1942 the Germans altered the Panzer IV significantly, doubling its armour and giving it a Pak 40 based gun. The T-34/76 had lost it's advantages against them. And obviously the Tiger I had no trouble with the T-34/76.
The T-34/85 didn't improve the armour situation as far as I know, it just allowed the T-34 to engage on equal footing with the Panzer IV, and Tiger I if it was close enough.
Honestly, when it comes to comparing a tank vs a tank, people get too wrapped up with tank vs tank fights.
Tanks spent 90% of the time fighting infantry, not other tanks.
And honestly, the t-34 was not really a good tank in 1941/ Why do i say this? Very unreliable. T-34s in 1941 had massive reliability problems, had lack of proper trained crews, and a huge lack of spare parts. Yes, of course the design was evolutionary, but that doesn't change the fact that the t-34 didint do much in 1941.
Same goes for the panther. An amazing tank on paper for 1943, yet when it was introduced it ended up a failure. Panthers only started to get good in 1944 when they started fixing the reliablity problems.
It's actually funny that the sides that had inferior tanks at the time were the winning ones. Germans in 1941-42 inferior tanks yet massive victories. USA on the western front 44-45 had arguably "inferior" tanks yet managed pretty much a 1:1 ratio when it came to losses.
Also about the PIV the PIV didin't get "double armor". It got a hull upgrade from 50mm to 80mm, while the turret remained 50mm. And the hull could be penetrated at 500~ meters with APCR. From what i understand the soviets were actually the side that managed to get APCR ammunition to reasonable quantities on tanks, especially later in the war.
And the t-34/85 did get an armor upgrade , the turret went from 70mm to 90mm. Not to mention the massivelly improved gun againts both infantry and armor, the 3 man turret.
Why did i write all of this off topic nonsense