I've updated the calculator with datamined data, added small performance and style improvements plus link to diablofans in the resources meta. It should calculate little bit faster now.
Let me know, if you find bugs (flexbox for example doesn't work in all browsers)
This is *not* correct, as people found out when leveling past paragon 2000 on PTR. After 2000, paragon per level doesn't increase anymore but stays the same. I added an updated version of the paragon chart to the end of my thread here.