One thing that D2 teaches me.

 This idea is not original from D2, but I understand it by D2.

And this idea is related to the two books I mentioned before. It makes me to understand the books immediately because I know this. 

So let me show directly. The thing is simple that the world is not continuous, it is like stairs. This is what I learn from D2. At the time I was a softcore player who didn't know the settings of D2, which made it a classical. I didn't know how Fast Caster Rate work, I only knew that if I got a 10% FCR ring for my Sor, I would cast faster. I didn't know why it doesn't become faster if I got 20% FCR until I found the data. And it seemed to be a shock to me as I read the Frame sheet of every career. Because I thought that it should be continuous before. But it was not. It was like stairs, if you didn't exceed the number you could not reach the next frame.

This idea was integrated as I read The Black Swan: The Impact of the Highly Improbable. What worked in D2 also worked in the real world. So there are something in common. And here is why the extreme scene is different from the common. For example, a slight difference would be nothing when you are not in tough maps like River of Flame in TSW mod. But it have a tremendous effect in such maps. So there would be a huge difference between people who are in tough maps or not. In reality, it is the same.