Formulas
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Status Effects
$$ \begin{aligned} MIN(BaseDuration * (1 + StatusEffectDurationReduction + TargetStatusEffectDurationMult) * \\(1 + EffectDurationMods) + TargetStatusEffectDurationMod, DurationMax) \end{aligned} $$
Damage
$$ \begin{aligned} Weapon Damage * Skill Modifier * (1 + BaseDamageMult - BaseDamageRed + [CRIT]) * \\(1 + Empower - Weaken) * (1 + AmmoMult) * (1 + MobWKN) * \\(1 - (ArmorMitigation * (1 - ArmorPen))) * (1 - (ABS + ABSVitals)) \end{aligned} $$
Armour
$$ \begin{aligned} ArmorMitigation = 1 - 1 / (1 + ArmorRating * (1 + [200con] + Fortify - Rend)) / \\(WeaponGS+DefendersAvgGS-AttackersAvgGS)^1,2) \end{aligned} $$
Weapon Damage
$$ \begin{aligned} BaseDamage (MasterItemDefiniton.ItemStatsRef |> WeaponItemDefinition.BaseDamage) * \\(1 + StatScaling + LevelScaling) \end{aligned} $$
Healing Threat
$$ \begin{aligned} threat = (damage + healing * healThreatMultiplier + blockedDamage * blockingThreatMulitplier)*\\(1+MAX(SUM(ThreatDamageFromPerks), -0.99)) \end{aligned} $$
Damage Absorption
Credit to Mixed Nuts.
AF = Affixes (Gems)
SE = Status Effects (Fortify via healer, abilities, oakflesh or gemstone dust)
ABSVitals = Ward potions
MIN(MAX(AF+SE,MIN(AF,-0.3)),MAX(AF,0.5))+ABSVitals
Put simply, your absorption is: (AF + SE) + ABSVitals
AF + SE is capped at 50%, unless AF is over 50% as mentioned above.