Tenacity certainly isnt parry levels of bad, but its still pretty bad, unfortunately. Its only real use is for Ultimate prog as there is the infinitesimally small chance that you might survive something with it just barely, but otherwise its useless everywhere else, especially in dungeons and extreme trials where the damage is rather minimal and proper cooldown management (Read: being good at your class) should be the solution and not melding tenacity.

It is however, simply just the way its designed. It increases self healing, damage, and reduces damage taken, so understandably its weaker than DH or crit...But i mean, the game is designed in such a way that means that the only real threatening damage to tanks is tank busters, thats why healers can dps so much of the time.

One thing they could do, is removing tenacity as a substat built in to gear, and only have it available to meld, and beef it up a bit so then atleast there would be some decision making as to if it should be melded or not. They could also remove the extra damage done part, and make it a purely defensive stat...But that'd be very easy for it to fall in the same pitfalls parry did.

It was a good idea, Tencity, but as it currently is, it simply wasn't meant to be.