Is there some aspect of this or the math behind it that I do not understand? If it reduces the damage that you take, that is good, right? Or does it only reduce damage to me if I would otherwise get a mortal attack against me?
Hopefully I don't get harrased here for giving an opinion
The ring itself is just straight up, honest damage reduction, both physical and magical.
It's also not your only source of damage reduction, so you stack it on top of other forms of damage reduction, there's a lot of them
Evasion, shields, armor, utility, buffs and debuffs, sustain. All those things are enhanced by the ring of tenacity.
It's kind of the same logic for the warrior Hold fast ability (3-6 armor) and the warden's Barkskin ability ( 0-150% of her level, it goes up to 0-45 armor at level 30)
Even if the Warden blocks significantly more damage, the warrior gets more benefit from the extra armor since he has a passive shield to back it up
It's literally the only... wait, excluding elements, I almost forgot that clowny clown ring.. only defensive ring without counting clown clowny ring in the game, ofc it's the best defensive ring in the game.
If it wasn't fundamentally flawed and just putting those upgrades in your armor making the damage reduction not only more effective but also giving you the possibility of having a better ring (literally every other ring) maybe I would like it too.
Just dodge the attacks. They are more punishing but avoidable. Once you have enough skill, you won't need to resist them, because you'll just not get hit