I have been pondering how exactly the Dark Eldar would distinguish themselves from their more...puerile cousins on the battlefield.

So how exactly do you think the Dark Eldar will differ from the Eldar in terms of combat? Would they be faster, would they deal more dmg? And what unique classes and abilities do you think they will have.

Posion. A lot of it.

Spikes

By not showing up for a long long time if at all

Seems like maybe the easiest of any new faction to add. Copy some Eldar assets with a little tweaking. Easily made Warriors and Scourge? What would the support unit be?

Bondage and melee...my kind of party.

Uhh Warriors, Scourges, Wyches/Incubi.. They would be a very melee oriented faction with Poison on EVERYTHING.. They don't really have any Heavy Support equivalent infantry.

It'd actually be super interesting to see them in game at some point.

Indeed.

Curses and dark spells of pain!
Hellish weaponary and vicious screams!