In the latest version (18.104.22.1683) released on 03 MAR 2015, body armor has ceased to function properly. Regardless of the armor a character is wearing, they absorb damage as if they were wearing full armor, even if naked. For example, it takes 3 Katiba shots to the chest to kill both a fully armored and naked target. It doesn't matter if you wear body armor or not, it will always take 3 chest shots with an assault rifle to kill you. Behavior is the same regardless of weapon used.
See the following screen shots for a demonstration:
You can see that it ALWAYS takes the same number of shots to kill a target regardless of the body armor they're wearing, if any.