No you are just quoting Fanfic what I just quoted you is what Meta is in the RPG nothing more nothing less it’s just a buff to caster level it is nothing at all like Wow’s meta.
again your making up fanfic. Essence is just magic power in the RPG demon hunters take in demonic magic and turn into demons they have nothing to do with souls the “ personification of any demon” or any thing else like the Wow demon hunters.Call it power, essence, soul, energy or whatever. It is still the personification of the demon.
They don't turn into demons by gorging on fel energies. It's by absorbing the power of a certain demon. His essence.