Just in case someone hasn't already fully answered.

Sometimes.

There are PLENTY of fights where controlling eos is entirely or 90% unnecessary (a outdated example.. but Garuda HM. Poping rouse + illumination + whispering when the 1st set of adds spawn is good and helpful. But before/after you could just set her to sic.


Some fights though... It will be HIGHLY beneficial for you to control illumination / whispering (such as fights that have long periods of no AE dmg where she will waste whispering if left to her own devices)

Especially if there is no WHM present as eos is a large majority of your group healing capabilities.