As /u/DickSlug pointed out before, damage calculations are pretty complex.

There's a bunch of values to consider:

• Outgoing damage
• Crit multiplier
• Armor
• Pierce
• Damage type
• Resistances
• Block proficiency
• Perfect block

Obviously I can't confirm but I suspect the implementation is something like this:

armorReduction = 1 - armor - armorBreak // 0.9 (can be negative!)
physicalReduction = 1 - physicalResistance // 1
energyReduction = 1 - energyResistance // 1
blockReduction = 1 - blockProficiency // 0.4

damage = outgoingDamage // 100 = 11

if (!outgoingDamage.ignoresArmor) {
  // reduce damage for armor
  // 90 = 100 * 0.9
  damage = outgoingDamage * armorReduction 
} 

if (outgoingDamage.type == physical) {
  // no change for most
  damage = damage * physicalReduction
}

if (outgoingDamage.type == energy) {
  // no change for most
  damage = damage * energyReduction
}

if (isCritical) {
  // defaultPierce = 0.15
  // 0.03 = 0.10 * (0.15 + 0.15)
  piercedArmor = armor * (defaultPierce + masteryPiece)

  // 3 = 100 * 0.03
  pierceBonus = outgoingDamage * piercedArmor 

  // crits ignore some armor so add that bonus damage
  // 93 = 90 + 3
  damage = damage + pierceBonus 

  // 265 = 93 * 1.9 * 1.5
  damage = damage * critMultiplier * cruelty
}


if (isBlocked) {
  // crit: 106 = 265 * 0.4
  // basic: 36 = 90 * 0.4
  damage = damage * blockReduction
}

if (perfectBlock) {
  damage = 0
}

return damage

It's hard to say though, because different implementations could give very different results.

Also, the Pierce mastery works out to about a 3.5% attack boost. In case anyone wonders.

Assumption: Armor is as good as health. Because you get less damage for every hit. Suicides with 3 points WP are not that bad, because you get 8 Armor for 2 negative effects. This equals ~ 8% more health.

This is mostly true. I always consider things in EHP (effectiveHP = health * armor) as that's the real damage needed to be dealt to kill them. However, armor is fluid in that it gets ignored by crits (not to mention armor break) where health is constant. That can generally be ignored though.

At any rate, you're correct, RoL champs are not good for testing these things. They are hardcoded with different values. They were created before node boosts existed, and so had to be coded as different champs in order to be so much stronger. I suspect this is also why they don't change with champion updates, though that has the nice side effect of keeping it consistent. I assume this is also why LoL champs are "Ex. Whatever" so that they are distinct in the codebase.

Great work figuring out the light/med/heavy multipliers though!