The accuracy/scatter of HE rounds is so bad
The Sherman HE shell has 6 scatter angle and 5.5 scatter max, which is actually significantly better than comparable units like the OST Panzer IV (7.5/6.4), T-34/76 (7.5/6.9) or Cromwell (7.5/6.4) and on par with the OKW Panzer IV (6.5/5.54), but all of these have vastly inferior AOE values. Without going into detail of how scatter works, in short, the lower these numbers the better.
There is also no statistical basis for your claims that Axis infantry has better DPS/accuracy or that they are effective at all ranges. Generally speaking Allied (mainline) infantry (except Cons) is statistically better across the board, although also more expensive to build and to fully upgrade.