On my magplar i use shards and BoL and sometimes ritual of ret (depending on the dungeon). Any other heal comes from resto staff tree.
Shards can be interchanged with by orbs
Ritual of ret can be interchanged with by blood ritual
And every class has some kind of class healing spell to compare to BoL.
I wouldn't doubt that nightblades probably make better healers but why would you take the unquestioned strongest dps class and use them as the least needed position (healer)?
Orbs give resources back to allies. You have option to use purge from alliance war too. Nightblades have best dps as healers, nice ultimate generation, major valitity, impressibe defensive ultimate. Long ago, they were 2nd most popular heer for dungeons.
I want to listen alcast answer