the 34/76 needs a buff against infantry (better AoE) coupled with the swap. the idea being that t3 has a tough AI vehicle pair with a weaker (hp/armour wise) AT vehicle while t4 has a tough AT vehicle coupled with a weaker AI vehicle. there's also differentiation between the two tiers with their respective 3rd units, infantry support in one and artillery in the other.
T34 can have miracle shots, increasing AOE is not the way to go. The 'bug fix' where the reload was too long should be removed. The t34 was in a good spot then.