I personally think ISU has more micro tax in order to be very good. The HE explosive shells are more damaging with ground attacks and many players do not utilize. Not to mention you have to switch shells between HE and AT.
Umm, no, they are not, its pure observation bias.
ISU has pretty significant scatter, so its pure RNG, it ain't brummbar where ground targeting helps anything, unless you're trying to hit blob on the move.