3% haste is generally better than nothing at all, and as ruskie mentioned it can help with openeres if, especially if you're lagging or low on SS. Also Fey Carress at worst case can still be used to cleanse of Pacification, Poison, etc. off a single person and you'll save a GCD on it.
I wouldn't use Eos unless your healing partner in 8man asks you to (or solo healing it), but if you prefer to use her on any content at least use her on Obey. Can't stand seeing Whispering Dawn > Fey Covenant > Fey Illumination going off the first second of a fight (and in an order that makes no sense).