i havent heard that bug being around in a long time. You can die, and not see explostion if someone is popping you from the back. There still may be a "hole" in the armor model, and I will have some of us beta look at it..but you are the first guy I've seen post on this problem, including the game forums.What tank were you in? But just because you saw riflemen and was dying, doesnt mean they were the ones killing you. If you were watching the riflemen, some sappers or the AI AT, or another tank could well be whacking you silly. The damage sounds are very similar for sappers and armor.
They may have hit you with 8 grenades, set the tank on fire, all sorts of possibilities,including a bug.
hardcase