But there is an interesting twist to it.
Indeed, when unperked, the M4(76) dominated the ground war for a short time. When it was slightly perked (along with the T-34/85) the usage was cut back to a still high, but 'acceptable' level, and remained at that for a long time
However, for reasons that are not yet entirely clear to me, the M4(76) usage suddenly radically dropped not too long ago. Despite being still a very good overall medium tank and with still a very good tank combat K/D.
Compared to when I left, I've noticed a lot more people are using the T-34/85, citing HVAP. Based on their tactics, it seems they are going for the few quick kills then die method.
The biggest reasons I oppose unperking it are; it is the toughest true medium tank, as far as actual damage it takes to kill one, this being due to the wet storage.
Second, it would require unperking the T-34/85, as you said. this would kill Panzer IV usage, warranting 30 ENY, and maybe 40 for the F2. Then you have the problem of everything else being all messed up in ENY, etc.
Just a big mess for reasons of current popular play style.