Overall army balance is irrelevant when singular units underperform.
All units should be viable choices, not always optimal, not always go-to option, but not useless to the point you wish you could travel back in time just to stop yourself from getting one.
Flak, M-42, greyhound, penals, vickers UC all suffer this fate.
In this particular case, scrap fuel cost or take away AoE, leave suppression and make it rely on accuracy instead of AoE and scatter to hit, this is the only way for such unit that does have gun on the ground level to hit anything when the ground isn't flat.
Agreed.
The other units that you mentioned should be fixed next.