Selene's usage in FCoB does have an impact on the overall party DPS, however, if you don't have a ninja to goad your physical dps it would ultimately serve as a dps loss as your bard would have to play paeon, instead of playing foe.

As a SCH, you could be dpsing the boss or add while having eos assisting your WHM with the healing with fey illumination/whispering dawn and putting out, ultimately, more dps than Selene impacts to the raid-wide dps while YOU the SCH is assisting with the heals. Since in the end, your bard would have to sing paeon longer and sooner due to the faster cooldown usage of invigorate, hastily decreasing raid wide dps - since as I have mention, could've been singing foe to increase magical damage.