DPS wise, using it on Shadow Flare is less of a gain compared to having to move and using SC on Bio II or Miasma or SF, so in mobile fights it can be best to save SC for movement. That being said, sometimes you can be sure you won't need it within the next 60s and should use it on Shadow Flare, which is a large portion of the fights.

Priority for SC: Opener > raise (if needed - as stated multiple times SMN is the last resort for raising in a coordinated group) > forced movement > Shadow Flare over raw cast if no forced movement in the next 60s