Board Thread:Warhammer 40k General Discussion/@comment-25507520-20150511012359/@comment-6078851-20150516132204

i wouldn't say that dark eldar are 'weak' as such, but rather they require very precise handling. their armour sucks since they're big fans of having as little armour as possible - less armour equals more agility - and they're the single most accomplished close combat fighters in the galaxy (wytches in particular). dark eldar are about speed and manoeuvrability but at the cost of durability - they have the worst durability in 40k.

in terms of how easy an army is to use properly: orks, imperial guard and necrons could be classed as easy to use, tau and tyranids i would say are between are medium, space marines and eldar could be classed as challenging, but dark eldar are expert. i've heard horror stories about how insanely deadly dark eldar can be if used properly. using them properly isn't easy though and i've also heard reverse-horror stories regarding their improper use which makes them sound like a joke army.

if you're going to use dark eldar as your 2nd army then i'd say be prepared to frequently loose until you get used to them - since your going from tyranids i would suggest using eldar or astartes before trying dark eldar: it's going to take getting used to having so few troops after tyranids, and at least eldar and astartes have a degree of durability :)