This is true, but i think “going toe to toe with demons dual-wielding warglaives” can more reasonably translate to tanking than it can with healing.
If they were to introduce a third DH spec, i think making us chaos spellcasters would make much more sense than healing. We could be somewhat like what hunters are in the ranged physical damage world - ranged mobile spellcasters.
Not gonna happen though. We won’t ever be given a third spec