Been playing the T34 L11, that tank is freaking undestructible unless you rush like an idiot into the enemies, but even that can work, I played a round on kursk, just ramming into people and oneshoting them.
T 34 F34 1942 is also really nice, quite easy to ammorack PzIIIs and IVs, very mobile but isn't as durable as L11 because the F2, StuG F and Pz III L can pen you, but with L11 you don't see those tanks often.
Either way, if some shell doesn't work on an Pz III/IV, just aim for the commander cupola with HE, it's insta kill, usually with the turret flying off. Yesterday I cleared my team's base wich was being capped by 4 tanks, just one-shotting them with HE into the cupolas, quite fun round