Here i have written one of many possibilities for a 3000 point Dark Eldar list.
3000 Points of Dark Eldar

HQ:
Archon w/ shadow field, crucible, punisher, combat drugs, haywire grenades, tormenter helm. 159
      10 incubi. 250

3 Hamonculi- stinger and scissorhands. 105.

Elites:
10 grotesques. 150
10 grotesques. 150
10 grotesques. 150

Troops:
20 warriors. 2 w/ cannon- 1 sybarite with poison blades. 191
20 warriors. 2 w/ cannon- 1 sybarite with poison blades. 191
20 warriors. 2 w/ cannon- 1 sybarite with poison blades. 191
20 warriors. 2 w/ cannon- 1 sybarite with poison blades. 191
6 warriors. 1 w/lance. on raider. 113
6 warriors. 1 w/lance. on raider. 113

Fast Attack:
10 Bikes 2 w/ blaster. 270
10 Bikes 2 w/ blaster. 270
10 bikes 2 w/shredder. 280

Heavy support:
10 scourges. 1 sybarite with haywire grenades and poison blades. 4 w/Splinter cannon. 255
10 scourges. 1 sybarite with poison blades. 4 w/Splinter cannon. 251
Explanation:
This list can be used very successfully. The tactic i picked to explain isthe slow ground advance.

Setup:
In the front row set up three picket lines of grotesques, to shield the incoming fire.
Put one hamonculi with each of them.

On either flank put a raider with the warriors.

Behind the grotesques arrange the 4 squads of twenty warriors.

Somewhere in that squad put your Archon and the Incubi.

Put 10 bikes in the center and on each flank, behind the warriors.

And put one group of scourges next to each raider.
Advance:
Now that your set-up, slowly move the whole line forward (excluding the scourges and raiders). Use the Raiders and Scourges to push fast up towards the enemies two sides, where they can weaken them with continuous Splinter cannon fire. Hopefully, they can break through and wrap around the enemy, but if not, so long as those flanks are weakened, you'll be fine.

If you playing a Ork or guard army, the low strength guns wont get past your grotesques, and so you'll have both the grotesques and warriors to assualt the front lines. Remember though that you should always fire at their whole line with this tactic, not just the center or a flank, because they could wrap you up in an envelope.
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