as a person who experienced the M4A2 on a pershing hull i say its kinda op for 5-6 battles since it has a early stab and it can mostly deflect shots at you so its for me an A or an S tier
The centaur set is crazy good, extreme mobility, but still enough armor to save you from things like medium caliber autocannons, (unlike the M18) and if you angle you can usually bounce a couple of shots from the higher caliber cannons. Definitely worth a try at some point.
T-34 should be S ngl i brought it to top tier and it can stand a lot of hits especially if you expose ur side then they will not know where to shoot give you time to see and shoot em
The 76mm freedom is very good, i used on t 35 and do his job, and even in tier 5 in a humvee hull do very well, now i use the tiger cannon on the humvee, is quite Op for being very fast and having fast transverse, and i have a tiger with amx 10 rc hull