Tbf
Only new spec I would really want is a ranged DH.
Just reuse WOD demonology lock and I would be happy.
Give me that W3 illidan meta back!
Beside that I would rather prefer if they gave us some more cosmetic stuff like green fire questline.
Fire for druids.
Dark ranger for Horde hunters where you willingly become undead, no clue what Ally could have in turn… Light forged hunters?
Dark shammans for shammans where all spells could be voidish.
In general, every class could have some light/void variant.
Just imagine holy bear or void kitten.
Or dark paladin
Or holy fire mage with all of the spells being holy based.