Bear in mind that BTM is not like armor, if you ever get to the step when you are subtracting BTM from damage then you always suffer at least 1 wound.
Kevlar has an armor rating of 2. This means that every weapon that does more than 2 damage inflicts at least 1 wound to the target, this includes SMGs, shotguns etc.
Also, a kevlar vest doesn't cover the arms. So 350 cr. would not be sufficient to cover the whole body with at least a rating of 2.
There are some overpowered combos, that's what also happened in the original Cyberpunk2020 (which the combat for this game is based on). If anything I nerfed armors a lot when making this game. The main advice I can give is that players going around with big guns and heavy armor ultimately attract the wrong kinds of people... with even bigger guns and heavier armor.