You're not being punished. Tenacity is perfectly fine to meld if that is what you like. There isn't a massive dps gap between dhit and tenacity builds, but you will lose a bit a damage for more mitigation. That's just the trade off. Unless you're in world first races, it doesn't matter what you meld anyways.
The bigger heals are compared to HP pools, the worse the defensive value of tenacity is. The actual amount of damage reduction you have to have to alter how healers heal is beyond what tenacity can provide, which means you're better off with one of the other options instead.

Its one of those great ideas that, in practice, doesnt work the way it should.