Whilst the % reduction diminishes, its overall effectiveness does not. Think about it - At 98% reduction, an additional 1% halves the damage you take. At 0% reduction, 1% reduces damage by... 1%. The more % reduction you have, the more valuable each additional % of reduction is. That's why the Armor Rating to % Ratio increases - to keep the overall value of armor linear.
My examples are valid. Firstly, you get 10% reduction from talents on top of the 40% from LW. That's 50%. Secondly, 50% is easier to calculate than 40%. And third, since we're working in %, and we're not looking at definite numbers but rather % change, I can use whatever value i bloody well like and the examples would still be valid as an example.second your example is not valid, because there is no 50% reduction of armor (last whisper reduce 40%) and because funktion is not linear, samples are behaving not linear (50AR - 30AR = 10,2 %difference), (100AR - 60AR = 12,5% difference), (200 AR -120AR = 12,2 %difference) and so on
As I said, more armor means LW removes more. But it is still super effective. And linear.