T3 has no place for t34, T3 is fine as it is and better than ever.
T34 is really bad right now, no matter how cheap it is, it fails to make anything useful. it needs to be doctrinal and a new role/vet ability.
T4 needs the t34/85 because soviets lack a lot of strength in late game, and they see themselves obligated to use commanders with late game units, all the other commanders become useless and not viable.
Kv1 needs stats in line with similar tanks, definitely some hp but its also really bad making damage against armour and infantry. Also it needs this for vet 1:
And if it still underperforming (i don't think so) then add this for vet 3:
historically acurated:
https://en.wikipedia.org/wiki/Zinoviy_Kolobanov