Well one thing's certain, the halftracks are too weak. If you're lucky enough to get a grenade IN the halftrack, or do an airburst over it, then that should obviously kill/injure the passengers. But the reality is, all too often explosions on the ground NEXT to the vehicle kill the driver, gunner or even passengers, right through the armor.
Also, the shield for the machine-gunner in the German halftrack is pretty useless. I base this opinion on my experiences manning the MG myself, and also fighting others who use it. As a rifleman, more than once I've shot and killed halftrack gunners from the front, right over the shield. And that's with a rifle. If you have a machinegun, all you have to do is pepper the top of the vehicle with bullets and one or two will get through, it's easy to do and the gunners barely stand a chance, unless they can get fire superiority and keep their enemies pinned down, but that's hard to do because of the way the (useless) shield limits their field-of-view.