Heres an explanation:
Back in time, precisely in the war of the ancients, the sisterhood of elune, normaly peacefull sisterhood of priests, turned into an paladins.
Why, u might ask? They fought in battle with weapons against demons, and in the same time healed their comrades, while wearing plate armour.
THIS looks like night elves paladns back in history! So why there isnt't night elven order of zealous fighters of elune today? Why really?
They can adopt the game mechanics with the spells named "holy light" and "flash of light" , but lorewise they will heal with the power of Elune.
Tell me what u thing.