It's because, starting from HW, tanking was dumbed down so all the DPS wanabee could pick up tanking. However, encounters can be tuned (like in the 2.X series of patch) so that holding aggro, mitigating damage and having a true macro view of an encounter (eg what should be the core of the tanks gameplay) become a (fun) challenge.
Personally I don't enjoy at all needing to optimize DPS on a tank. If I wanted to do that I'd just play a DPS. That's also why I didn't partake in any heavensward endgame activities.
That aside, DRK and WAR need to be revamped in order to bring relevant utility to the group that isn't DPS related.