I'll get you space mahrens!

Running the Dark Eldar in the current environment of 40k feels like being a cartoon villain.

I make evil schemes that are way more complicated than it is to unravel them. Where I have to find the balance between speed, firepower, alpha strike, later turn objective positioning, the enemy just has to bring some mid strength guns to wreck my day.
I'm not saying that I don't win my fair share of games, but when it comes to a competitive setting my dark eldar just don't get the job done at the top tables.

Turn one everything seems to be going to plan, the enemy hug their foxholes as dark light weapons, blast templates, and poisoned shots rip into them from all angles. The assault elements are quickly moving forward and will be on the enemy next turn so difficult choices need to be made.

This is where the dark eldar are supposed to be, sewing terror in the enemy and making them try to decide between poisoned darts or poisoned blades at the method of their deaths.

But for the last few months it seems the armies of 40k have adapted to better deal with the pressure that we can put them under. Here's a list of what I have been having issues with here in my local meta and theories on how to get around it.

Coteaz and his "I shoot at everything coming out of your webway portal" special rule.
This guy and the squad he is with get the ability to shoot at anything that come on from reserve within 12". So it doesn't matter how many units you have coming out he gets to fire at all of them.
Honestly I really don't have an answer for this other than to watch where you place the webway portal. Set it in terrain so you will get a cover save from the incoming fire, on one flank so coteaz and his unit cant get to it until it is too late to stop the wyches or beasts coming out. Or what I have done in the past when I knew my opponent is going to use this tactic is to put 1 Talos in the portal and give them a big surprise when he comes out and charges Coteaz's unit *evil smile*

Dark lances having a hard time doing anything to the enemy.
With a lot of the mech style armies showing up with AV 11-12 the lance weapons that our army leans on aren't as scary to them anymore. I know the dice gods have not been smiling on me lately I can go whole turns without doing any damage to my enemies vehicle park. A way around this to have a almost guaranteed "stun lock" on your enemy is the humble haywire blaster and haywire grenades. Haywire blasters have the ability to glance on a 2-5 whenever they hit increasing the effectiveness of the haywire grenades by making them auto hit on a stunned, or immobilised target. They are hard to come by in the dark eldar codex available on talos and scourges. If you go for this tactic I would suggest to take a single squad of scourges to supplement your regular anti tank to take care of that one enemy vehicle that you just cant let fire. Also the grenades on the wyches are an excellent cheapish way to get them into the fight and can give them a chance when they have to charge a walker.

Necrons jumping around everywhere.
Ive seen this come up in vassal games and started to show up more in the meta as the new necron fad. They have the ability to deep strike around every tun and keep the enemy at arms length.
This is where the absolute speed of the dark eldar comes in. The necron unit has to stay roughly within 24" of a unit to get shots after they jump. That is roughly the threat range of any close combat unit in a raider and your beasts. Beasts will just wreck necron face in close combat and probably break them and if all you have close enough this turn are some warriors in a raider or venom I would still throw them in there. Because once the necrons are in combat, there is only one veil of darkness that can get them out of there. Then the next turn send some close combat unit into them for support.

Grey Knights henchmen, psyfilemen, razorsapam....

sorry I still got nothing for this, at least nothing that works consistently. Hopefully your dice roll warmer than mine and you can get some damage on the dreads and get to grips to the soft squishy parts of the army before they blow you out of the sky.

There are a lot more little things that have cropped up that will give a Dark Eldar Archon indigestion, I could make this into an even longer wall of text but it just comes down to playing, losing, and learning from your mistakes. Don't get discouraged after a close loss or draw just walk away from the table shaking your fist and yell "I'll get you Gadget!!... meddling kids."

there are always more souls to try and steal.

Stay thirsty my friends