The thing is, unless you somehow actually have no use at all for Eos's higher healing output (and seriously, how are you not finding a place to use Whispering Dawn?), in most situations you'll get a higher rDPS increase by freeing up yourself and your cohealer to spend more GCDs on DPS, than you would with Fey Wind. The way the math works out, Wind by itself isn't actually a DPS increase until ~60sec (3 full durations) under it's effect - before that it's front loading your damage slightly, but it takes that long for the extra speed to actually let you get an entire extra global in. And that's assuming that there is no clipping or globals lost to movement while Wind is up.
The spell as it exists right now is really only useful for squeezing an extra attack into opener raid buffs by using it pre-pull like FalalaMaru mentioned.
