As we all know MMORPGs are all about numbers. If someone is seeking meta builds and optimal group compositions for maximum damage, sustain, and reduction of time for a given dungeon or trial, why bring a DK?
This is something that Zenimax needs to consider when balancing classes. The imbalance and nerfs mainly impact the upper 1% of players doing Trials, Vet Trials, and Veteran Hardmodes. Of course, anyone that just runs around the overland and does normal dungeons will never care about the DK Nerf and likely runs some weird combination of gear.
The DK has no role besides tank once this goes live. Even the tank role is being contended for by the Warden. I understand Warden isn't a better tank but if any more changes occur it could be.