Can be, but seldom is. You do need to read up on the Eldar, though.
LD8: Guardians (just plain bad), Rangers (dead in melee regardless), Jetbikes (dead in melee against fear units anyway)
LD9: Everything else that isn't a real
HQ.
LD10: Anything with an
HQ.
Fearless: Any with a Phoenix Lord, Wraithlords, Wraithguard and anything within 12" of an Avatar.
In my experience, Fear is a tool more useful to the Craftworlders than it is a tool against them.