Right now there are 12 DH tanks in top the top 100.
As per damage comparison. DH outshines Fury hardcore in Raiding (DH 9 vs Fury 19) and is barely barely barely behind Fury in M+ (DH10 vs Fury8).
I dont see your point in DH bieing weak, they are overall a far more adaptive and stronger class than Fury atm, let alone Arms (omg).
The only reason Fury even gets to play this game is because of the utility (that again DH has plenty of aswell)…