Oh, if only someone had written a
tactical series about grouping Eldar and Dark Eldar together for fun and shenanigans.
Personally, I dislike Wave Serpents. If you're running with Dark Eldar, use the Raiders. Warwalkers aren't impressive, and Wraithlords are only so-so.
Fire Dragons in a Raider are awesome. Mushkilla on the Dark City wrote a good article showing how to Deep Strike them to best effect (you can completely circumvent Imperial Knights' shields, if you do it correctly).
I absolutely recommend Scatbikes for your troop tax, and Farseers for your
HQs. If you
don't want to go with the Freakshow route, then Crimson Hunters are absolutely dynamite units to bring. Wraithguard are another unit that goes well with Dark Eldar, since our Open Topped transports give them greater mobility and a better firing platform. Webway Portals are also a tasty bennie for any unit that an
HQ can accompany. If you're looking to add anti-tank, I might also point you in the direction of Swooping Hawks.