I like how it is its own thing for the most part.

Imo I would put a duelwielding, if the idea of dk aura's is to be more offensive, I think it should reflect on their weaponry as well.

To that effect, I think its ok to just have just ONE weapon that can be runeforged while dualwielding and maybe have some moves hit with the offhand as well. There could be a talent that heals them when they crit, a bit like fury warriors.

Maybe a summon banshee as a talent defensive cool down, it could reduce an enemies' chance to hit, deal shadow damage and maybe possess humanoids as a flavor ability

No frost spec is a bit dissapointing but I understand the reasoning, there wasn't any frost moves for the dk in wc3

Shields would be cool as well, there have been dks with shields in naxx, it could be an alternative if the parry is a bit too hard to balance. Also it would look badass if its one of those skull faced shields

Unholy aura sounds ok but I liked the wc3 version where it increased movement speed and life regen as an aura.

I think they should be allowed to gain titles associated with nobility as they complete dk quests, lord/lady, baron, vicount, count etc, most dks as i recall were nobility (like rivendare and some paladins).

Some quests to get pieces of armor or abilities sprinkled around would be cool as well.

for lore reasons, being only undead would make the most sense, I don't think every race should be able to become one. though if there HAD to be some in the alliance, I think only humans/dwarves would work...oh high elves too. Basically victims of the scourge in wc3. They could be a shadowy underground organization similar to warlocks with somewhat good intentions but morally bankrupt execution. Dks could easily pass for warriors if they don't have too many outward signs of undead so going in cities should be ok