Normally, we aren't too keen on posting exploit or unpatched bug videos but this is one of those cases where this seems to be a rather high priority issue that needs to be fixed ASAP. So, the more people that are aware of this, the better the chances are that this issue gets resolved for Battlefield 4, right?

The short of this bug is that a hitbox on a body that can be revived remains where it shouldn't be. This prevents most projectiles from passing through to anything behind it, including grenades, rockets, and even tank shells. Thus, a player behind this hitbox "death shield" is impervious to some types of damage.

Perhaps this explains some oddities you've encountered when playing Battlefield 4, because this sure as hell explains quite a few things from my time playing.