In the last weeks I really came to think about Dark Eldar as both Eldar and Corsairs actually seem to be faster and harder hitting than we are. You seem to be thinking about which way the army should go, so I thought I' share what I've been thinking so far.
We could just go for "even more speed, coupled with even more firepower", but I think the strengths of Drow/Dark Elves is that they are finesse armies and we should be too.
I just don't like the feeling that we become more like "Kinky Craftworlders" in bikini armor and big guns.
We should be different, we should be the dark elite that does not win because of big guns but because we got means to bend the rules of the games to our advantage and have gear nobody else has access too. We are the eldrich abomination that lurks in the shadow and has every kind of trick up its sleeve.
We are known for speed and while we have adequately fast units it seems like almost everybody has its fair share of fast movement as well and we can't get an edge with just speed anymore.
And as it stands, our strength is fast deployment and web way portal shenanigans, so what if we try to capitalize more from such things? Don't forget the reason we got poison and lance rules is because Phil Kelly wanted an army that "cheats".
I think more poison, lances or more firepower in general is just no our style, we need more "cheats".
In that regard I like that you thought of giving Wyches infiltrate, but I wouldn't Hellions (as Troops) maybe not more suited for this?
Anyway, things I could think of:
- Directly assaulting with melee units the turn they arrive from Deep Strike (let us purchase a rule on transports for that matter)
- More pinning weapons, like "pinning Bolters" for Warriors, so our melee units don't have to fear overwatch
- Let us pay for the ability to half/reroll scatter distance of Jumpjet units or vehicles
- More units with Outflank + Acute senses
- Gives us weapons that deal damage to units inside
- Anti bike/vehicle template weapons for Coven (did I hear corrosive liquifier?)
- Reserve Manipulation is a must
- We have problems with "Ignores Cover" weapons, so let us have a "Shadow Disruption Field" that nullifys the effect of ignores cover.
- Grav weapons for Coven (considering everything they have, Grav would almost seem "mundane")
Now, the Codex you have made already has potent stuff and if we would put the things I just mentioned on top of it, it would be op. So, I am talking about this from the standpoint of our current Codex but I thought you be inspired by some of the ideas.
All I wish is having back the "Terror" Dark Eldar are supposed to spread on the battlefield and let us feel like a master tactician while we orchestrate the rules of the game to our will.
Btw. I love that Pain Engines can have the Deep Strike rule for that matter.
And regarding your Dark Lance thoughts, I think the idea of a "Dark Laser" which I've seen in another fan dex would be a really great addition to Dark Eldar in general: https://1d4chan.org/wiki/Codex_-_Dark_Eldar_Angry_Emo_Edition
I also got an idea for Hellions. What if they had "Envenomed Blades" on their Skyboards that can be used as a weapon as well? It could generate extra close-combat poison damage every time this unit charges or is being charged. It would pair well with Hit & Run in that regard.
And I too think a spirit probe would be more fitting on a Haemonculus than the PFP + 1. But I would advise to remake the Haemonculi in general, as I've said in the past already