Hey there, glad my first post here can be dispensing some friendly, if general, advice. If you want I can give more specific advice based on your list but I feel most DE armies need to consider the same basic things!
#1: Cover. Remember carefully hiding your plague marines (I'm boldly assuming you didn't run csm with marks) whenever low AP weapons were about? Yeah, do that all the time now! One you're out of your transport you need to put stuff between you and your opponent so he doesn't gun you down. This includes LoS blocking terrain for our vehicles. Speaking of vehicles...
#2: Flying coffins. I love DE vehicles, always have! They're one of the reasons I first picked the army up all those years ago. That said staying in them is basically a death sentence för your troops. Your vehicles will be very fast which can lead you to inadvertently position them in very bad spots, so knowing where your firepower needs to be and when to disembark your troops is essential.
#3: Secondary Objectives. Dark Eldar are much better at claiming secondaries than primaries, at least in my experience. Your mobility will allow you to easily claim linebreaker, your guns will easily secure first blood and your archon is killy enough to murder most any warlord in a fair fight (which you will never, ever give it). Your mobility also ensures that you will be able to deny your opponent objectives by driving up to him in the last turns and contesting. This of course doesn't mean that you shouldn't go for primaries if you can, but remember that sometimes you gain more from crippling your opponents scoring.
"What shadows we are"