I think it's fine as it is. The only difference is that they need to nerf handheld AT especially shreks on Volks.
The problem comes from the fact mediums cannot effectively flank OKW heavies to block/ram shoot in the back because volksblobs can effectively one shoot a lot of medium tanks. Another solution would be to make medium tanks still drive relatively fast even with damaged engine.
That was pretty evident in last days Lennys game.
Lenny had SU-85 and 3 T34/76, he faces 2 shreck volks, 1 puppchen and 1 KT.
He managed to chase off volks and kill puppchen if I remember good, but KT wrecked every single piece of armor he had without ever going below 50%, that includes tanks blocking its reverse and shooting on its arse.
While that wasn't speed problem, but more of volks and KT being impervious from all sides to SU non doctrinal armor in this particular case, the general speed of heavies still prevents any flanking attempts when heavies are on the move and scoring engine damage on them is challenging to say the least.