Now I realize that I should have spent some points in tailoring to craft metal armor (WTH)
Well, it's not like you can just slap metal plates on your naked body and call it a day.
But anyways, in case of metal armors, the carrier vest is the only component that requires tailoring and its quality doesn't affect your mechanical damage resistance/threshold, only whatever bonus the particular vest gives (bio DR/DT, cold DR/DT, electricity DR/DT, bonus health or health regeneration) and durability.
So you can get away with putting very little points into tailoring to use low quality vests if you odn't care about those bonuses, but if you want to focus on armor crafting then you definetly should put at least 100+ points into it.
Also some points into electronics if you want electricity DR/DT, chemistry if you want bio DR/DT or biology if you want health regeneration but not much.