Duster + Flak Vest sometimes worse than Flak Vest alone?

[ruckenhof]

As far as I understand armor system in 1.0, bullet has a chance to be deflected/mitigated according to Sharp armor value. On mitigation it proceeds to the next layer as blunt damage (while keeping "armor penetration" value).

That means that for high-quality vests, wearing duster over them is harmful, since duster often "passes down" a mitigated blunt bullet, and vests suck against blunt. Let's assume bullet with AP 27% (standard bolt-action) hits a pawn that wears excellent thrumbofur duster and legendary flak vest underneath. Sharp armor of a duster is 81%, while sharp and blunt armors of a vest are 180% and 65%.

Vest without a duster simply deflects the bullet in (180-27)/2 = 76.5% of cases and mitigates it otherwise.

Duster deflects a bullet with a chance of (81-27)/2 = 27%, has the same chance of mitigation, and passes the bullet unaffected in 46% of cases. In case of mitigation, vest deflects a (now blunt) bullet in (65-27)/2 = 19% of cases and mitigates it for the second time with the same chance. In case of being passed, vest deflects a (still sharp) bullet in (180-27)/2 = 76.5% of cases and mitigated it otherwise. So, overall result looks like that: 67.32% deflected, 27.55% mitigated, 5.13% mitigated twice.

I hope to be proved wrong, since I don't like it.

[Limdood]

3 things here:

1) why on earth are you wearing a duster worth like 2x the cost of another pawn?  It seems a poor practice to wear such insanely expensive gear with low stats.  A suit of marine armor is worth a similar amount or LESS and protects far more.

2) Skipping the duster doesn't bode well for your arms/legs in a fight

3) dusters are generally an environmental choice, rather than a combat choice. 

Finally, you used the stats on a legendary vest....it seems unlikely that you are obtaining a sufficient quantity of legendary quality armor vests for this to matter.  How do the stats compare on excellent quality gear?  say an excellent quality flak vest and an excellent quality plainleather or alpaca wool duster, which are much more plausible and practical for constant wear?

There are also 3 assumptions in here that may or may not exist in the game:
1) the assumption that a mitigated damage value is checked again.  It is possible that if a given layer mitigates damage, that the resulting damage is simply applied without checking any other layers.  This would make wearing ANYTHING outside of a (quality) flak vest detrimental.

2) the assumption that the calculation changes as the bullet passes layers.  It is possible that the initial bullet is tested against each layer for nullification, and THEN tested for mitigation against each layer....in which case layers would ALWAYS be helpful, as your highest armor value layer still gets to always apply, unless a different layer did an equal or better job already.

3) the assumption that the armor piercing value stays the same as the bullet is mitigated.  The damage of the projectile is reduced to half upon being mitigated to blunt damage.  It is entirely possible that the armor piercing value is likewise halved or may even be completely removed as the damage changes states.  A lower armor pierce on the blunt damage significantly increases the likelihood of the double mitigation.  That being said, the fact that many weapons have something OTHER than the base "armor pierce = 1.5 x damage" means that the awkwardness of programming reduced damage value armor pierce on many weapons points to either of the first two assumptions alternatives being more plausible.

[ruckenhof]

The first two assumptions are based straight on in-game tooltip and Tynan's explanation of the reworked armor system. The damage is indeed applied to each layer from the outside in and is calculated separately for each layer. The third assumption doesn't change much since halving AP still results in lowered deflection of duster+vest compared to vest only. Only full negation of AP results in vest and duster+vest being similar.

As for my example, it is purely theoretical. It's curious that certain armor combo behaves counterintuitively. It's only relevant for certain combos of material/quality, normal duster + normal vest are actually providing (very marginally) better chance of deflection.