What about more than 1 player is playing the same account? I am pretty sure that a lot of top ranked players are botting but i'm also pretty sure some of them might be sharing their account. 300h+ played time does not mean they are botting.
When I was young , I remember in D2 me and my brother used to share the same account. Maybe some of the top player are legit and are simply sharing their account. What do you think?