I disagree. The Cromwell was over performing. To a lesser extent so was the wolverine in comparison to puma. And I'm not sure if you noticed but the t34 just received a bunch of buffs.
The Cromwell is overperforming because its the first relevant Allied Medium. It still gets murdered to death by Panzershrecks, but now Faust Snare + Panzershrecks combined with huge Heavy-like size means its impossible to use its speed advantage.
I don't understand why you compare a Tank to an Armoured Car, but the M10 is an inferior Tank Destroyer, at premium cost with no AI ability. Crush gave it a slight bit of utility.
T-34 did get buffed proper at the start, but then they neutered it again, then they removed crush which is a HUGE loss of AI (despite its main gun not actually getting buffed).