Since the change with GLS being used to make an aug, here's the zones in which you can find them.
West Commons (not as many as NK, but they are closer together)
Qeynos Hills (only a handful)
Nek Forest (obsolete)
Jagged Pine Forest
Erud Crossing (looked, only found a handful)
Toxx Forest (looked, didn't find a single one)
WK
EK
NK (has most wisp spawn points)
Greater Fay
Befallen (random spawn on the bottom floor)
Have fun hunting your wisps
