HE is much more useful vs any GV that has "soft" armor when compared to AP. Namely, the M3, M8, 251, and jeep. Also, the Wirby and Osty can be turreted easier than one thinks with HE. Even if you miss, you still hit.
Yes, but given Aces High 95% will be loaded down with AP rounds on defense, where attackers will rarely see an M8/M3 defending a town (unless its a last ditch effort to get to the town)
I haven't tired a main round on a m3/m8/jeep in weeks - pintle a tire out and wait till the vehicle leans to one side - fire a few pintle rounds into the hull and they go boom quick. I have recently realized if you explode a HE round above an M3 it will explode - was firing at a town building and an m3 was next to it, we both wondered what the hell happened, I guess its a proximity death, he also had a tire shot out by a strafing aircraft.