If you can't understand gold value and diminishing returns, there's no helping you understanding this topic.
The only diminishing returns in the game are %pen(not sure about this one), dodge, MS and slows.
Incorrect. Armor and MR are technically diminishing returns. %pen is actually NOT a diminishing return. I am almost positive it stacks additively. Though, this can be tested with the 10% mastery and an item.
1.5% is literally just the same thing as 1.5 armour and mr.
Derrrrrrrrp.
A tiny fraction better vs penn and % penn, maybe.
Not correct. It's actually like 1.52 Armor at 0 Armor and then INCREASES from there.
Since the 1.5% damage is a reduction, that means you're effectively gaining more Armor/MR as you gain Armor/MR, since your Armor and MR are diminishing returns on damage reduction.
Therefore, at 0 Armor/MR, you have a natural 0% damage reduction, plus the 1.5% damage reduction means you take 98.5% damage. This would be the same as having 1.523 Armor/MR.
At 25 Armor/MR, you have a natural 20% damage reduction, plus the 1.5% damage reduction means you take 78.818% damage. This would be the same as having 26.875 Armor/MR.
At 100 Armor/MR, you have a natural 50% damage reduction, plus the 1.5% damage reduction means you take 49.261% damage. This would be the same as having 103 Armor/MR.
At 300 Armor/MR, you have a natural 75% damage reduction, plus the 1.5% damage reduction means you take 24.631% damage. This would be the same as having 306 Armor/MR.
You gain more Armor and MR from having more Armor and MR.
% penetration and % damage reduction are two sides of the same coin you numbnut. Also, every single stat in this game has diminishing returns. If not everyone would just stack one single stat forever and it'd be the optimal strategy.
Nope. AD has 100% returns, which some people DO stack. Health technically has increasing returns depending on Armor and MR.