I want to start speedrunning but categories need to be divided into difficult, hardcore or normal should be the standard for speedrunning.

Sorry, but we go with the minimum and hardest. Being how brutal the game is even going thru the first two acts is longer than the run on casual. For that reason Insane is not added because it's basically a walkthru.

If you want to play on the other difficulties then no one's stopping you.

I've passed around the idea for Classic Any% because after Gears 1 with the introduction of Normal Casual needed to be adjusted. The difficulty of Normal in later games is equivalent to Gears 1 Casual. And Casual as such was reduced in difficulty. Maybe this could be for special races or something for fun. But as a category some games have enough categories. Having another one just clogs them up and then add the Xbox One/360 split or PC/Console becomes more of a hassle.