In my experience and opinion Dark Eldar are better than ever this edition. That being said there are a lot of people on the internet who go around claiming the sky is falling, you will find these people probably haven't even played a game of 6th edition yet. It's human nature to complain.Common internet complaints about Dark Eldar:Hull point make our fragile vehicles even more fragile!
This is completely false in 5th edition dark eldar transports would never survive more then 2-3 glancing hits. In fact the opposite is true as glancing hits only remove Hull Point our transports tend to be more resilient against small arms fire this edition.FNP is pointless now!
It's not as good at protecting against small arms fire, but it now works against power weapons. Also on our tougher units, reavers, wracks, grotesques and Talos this is an improvement as it helps protect those units against power weapons and high strength/low ap weapons (this is especially good for the Talos in particular).Furious charge is usless!
Furious charge doesn't give +1initiative anymore, although this hurts coven units it has absolutely not affect on the rest of the army, who's initiative is already sky high. Furious charge still counters one of the Dark Eldar's weaknesses and that is being S3.Fleet is rubish this edition!
Fleet is huge this edition, as it lets you re-roll one or more dice, which means your average charge distance with fleet is 9" (57% chance of making a 9" charge). It also makes fleet models a lot more reliable at charging through terrain, the average charge distance through terrain is 8" (52% chance of making a 8" charge). With fleet you have a 93% chance of making a 6" charge in the open and a 82% chance of making a 6" charge through difficult terrain. Finally now you can shoot before assaulting which is great when you assault troops have good BS, plasma grenades, and splinter pistols. As soon as you don't have fleet charging becomes really unreliable making assault units without fleet a liability.Overwatch makes wyches unplayable!
Overwatch only hits on a 6. Now that fleet makes wyches very reliable at charging through cover there are very few reasons for them not to charge through cover, this will normally give them a 5+ cover save. If you take the PGL (defensive grenades now give you stealth within 8") they would have a 4+ cover save against overwatch. In short overwatch is not a big deal and there are loads of ways to get around it which I won't go into here.Things that the internet tends to ignore:NIght fight is amazing!
The changes to night fight make it combine really well with the jink saves the dark eldar army gets and the fact that Dark Edlar have night vision. Night fight also happens more frequently.Jink saves are amazing!
Now all Dark Eldar vehicles get a 5+ cover save just for moving making them more survivable (and also meaning you don't have to buy flicker fields). Reaver Jetbikes get a 4+ cover save for moving, making them a lot more survivable this edition. Jink also combines with the stealth/shrouding from night fight making the dark eldar army very hard to destroy when the sun is down.Rapid fire is amazing!
Warriors can now move and shoot 24" this makes them better when they are on foot and is also a nice boost to raider gunboats as they can move 6" and still shoot at max range.Wound allocation combined with Dark Eldar Mobility is amazing!
Now that wounds are allocated to the nearest model dark eldar have a huge potential to snipe important models thanks to their great mobility.Plasma grenades are amazing!
Plasma grenades are great as they can now be thrown and are S4 AP4 making them the best grenades in the game.Haywire grenades are amazing!
With the addition of hull points, vehicles only being hit on at worst a 3+, combined with stripping hull point wrecking vehicles haywire grenades have become one of the most reliable forms of anti-tank in the game.Changes to reserves!
Dark Eldar have no way of manipulating reserves, so reserving units was always a liability. Now with all reserves coming on turn 2 on a 3+, keeping units in reserve becomes a viable optionA lot of the army got faster!
A lot of units got a lot faster, reavers now move 48", our fast skimmers move 30", beast move 12".Assault vehicles are more important!
Now you can only assault on the turn you disembark if you are in an assault vehicles, this means armies like marines now can't reliably assault out of their transports (before you could assault as long as the transport didn't move).Lances are now better then missile launchers!
Now that AP2 matters dark lances are a lot more effective then missile launchers.
Hope that helps.