Regardless of the exact build, however, all battle-proven lists have a concept in common; use the Dark Eldar's firepower early and often to break tanks and the squads inside and follow up with close combat-oriented cleanup squads.
Here's my list for the Bay Area Open:
Vect
Haemonculus
8 Wyches (Hydra Gauntlets, Hekatrix/Agoniser)
Dais of Destruction
5 Kabalite Warriors (Blaster)
Venom (Splinter Cannons)
5 Kabalite Warriors (Blaster)
Venom (Splinter Cannons)
5 Kabalite Warriors (Blaster)
Venom (Splinter Cannons)
4 Kabalite Trueborn (4 Blasters)
Venom (Splinter Cannons)
4 Kabalite Trueborn (4 Blasters)
Venom (Splinter Cannons)
4 Kabalite Trueborn (4 Blasters)
Venom (Splinter Cannons)
3 Ravagers (3 Flickerfields)
My goal with this build was twofold; first, to find an effective balance between splinter and darklight weaponry in order to remain competitive against a variety of lists over a two-day period; and second, to cripple as many individual units as possible as quickly as possible, then to use the Wyches and Vect to clean up the remainders.
This list is a hard alpha strike list; it's vital that it go first regardless of the game type or deployment method since it has only ten AV units and six of those are vulnerable to something as commonplace as bolter fire. If, for example, I were to go second and lose only a single Venom full of Trueborn, my opponent would have removed 12 BS 4 poisoned shots and 4 Blaster shots from the game. Multiply that by the average of five turns that it would have survived had I gone first and been in a position to protect it and I've lost a total of 20 Blaster shots and a whopping 60 splinter cannon shots before the game's even begun.
In order to protect my ability to alpha strike, I've included Vect. He's a 240pt single model with the ability to seize the initiative on a roll of 4+. His improved seize does two things in competitive play; it scares half of my opponents into allowing me the first turn rather than risking a 50% chance that I'll seize and catch them out of position; and it also gives me a 50% chance to seize and catch my opponents out of position. Over the course of seven rounds at the Bay Area Open I was able to secure the first turn six times; the seventh game I won the die roll and chose to take second against an entirely deep-striking Tyranids list.
Alpha striking with Dark Eldar can be extremely difficult to accomplish. While each of my vehicles boasts a 36" range on its weaponry, my 15 Blasters have a range of 18" and my splinter rifles are 24" rapid fire. The key to success here is in the deployment; regardless of the scenario or its particular rules it's vital that you set up the entirety of your force as centrally as possible. In a tournament setting you're unlikely to come across an opponent who's eager to reserve anything and play at a handicap until it arrives on the board; instead, most players will either deploy in a corner as far away from you as possible or will mimic you with a central deployment. What I've found in extensive playtesting is that very few armies can (or are willing to) deploy entirely in the center of the board; most will concentrate the majority of their forces there and trail the remainder off to one side.
Your turn one should see each of your vehicles take advantage of their free rotation to gain an additional inch or two of movement, then move a full 12" away from any trailed-out units on your opponent's side of the board. The goal here is to remove trailing units from the early turns of the game and to focus fire instead on centralized units. Disembarking Trueborn units from a Venom that's used its free rotate effectively will give them an actual range of 34" and will give you (in the list I shared above, at least) 12 additional Blaster shots on turn one.
If your opponen is entirely mechanized you'll be using your splinter cannons to wipe out squads that fall out of broken tanks. If not, you'll need to focus your fire on long-range threats; Lootas, Devastators, and Longfangs all come to mind as squishy targets that should be high-priority for you.
By utlizing the combined firepower of all of your darklight weapons turn one, you should be able to cripple nearly any army you're matched up against. My list above has a total of 27 strength 8 lance shots on turn one, each of which can result in an Explodes! or Wrecked result for anything in the game short of a Monolith.
Aside from the fact that it's always fun to blow up as many targets as possible, your goal here is to leave your opponent with so few units capable of downing your own AV targets that you can predict and, in fact, control what they'll be shooting at. The Dais of Destruction in my list is the only vehicle to move 6" turn one, since it can't move further than that and still shoot all three lances; between the relatively short movement, the fact that it doesn't have Flickerfields and the threat level of Vect and a squad of Wyches, it should almost always be my opponent's first target. Since it has AV 13 all around and a narrow profile that's great for generating cover saves, it should absorb more than a single lascannon shot before it goes down. The trick here is that I want it to go down; better a transport carrying a unit with Feel No Pain and that's relatively mobile than a squad of Trueborn who can be entirely lost to a Venom explosion.
The Ravagers in this list serve a similar function; they're AV 11, which requires more firepower to down than AV 10, and they house less firepower than a single Trueborn Venom. Better that my opponent focuses fire on the three of them than my six multi-tasking Venoms.
If you're able to effectively alpha strike, you're not likely to lose more than the Dais of Destruction and a single Ravager on your opponent's first turn. When you follow up with the majority of your firepower still intact turn two you'll have taken complete control of the game; that's the point at which you unleash Vect and his Wyches and make as many multiple assault moves as possible in order to quickly accumulate Pain Tokens (which will increase your squad's survivability) and to sweep whatever remaining resistance your opponent may have right off the board.
