It's not a broken mechanic because it works absolutely fine. It's just you not liking that playstyle trying to grasp for 'arguments' against it.
Face the reality: Blizzard made very clear from the very beginning that using mobility for damage is an essential part of (Havoc) DHs. So, probably Havoc DH indeed just is not the right spec for you. There are a lot of other melee specs with very different gameplay that don't focus on using mobility for more damage. You have a choice: stop complaining and pick those that suit you better.