Here's something I've been thinking about for a while, even under our old codex.
Background: my friends and I tend to let each other know what army we're playing before we play, as it makes for a more interesting game (i.e., if I make an all rounders list, then my opponent plays his orks, I'm gonna feel my Dark Lances are a bit overkill, etc). However, I always seem to find that this seems to be more of a problem for Dark Eldar than my other armies.
Case and point: one of the last games of 5th I played was against a friend who said he was using Imperial Guard, I said I'd use Dark Eldar. He brought three Hydra and proceeded to decimate all my transports almost immediately, leaving me pretty much tabled by start of turn 3.
I'm not wanting to debate if list tailoring is good or not (I don't really care, I do it and I generally prefer it), but is it too detrimental for the Dark Kin? Does our glass cannon status cause more problems than it solves here?
TL;DR: Is it easier to build an anti-Dark Eldar list than other armies?