Originally Posted by
Alahra
Prior to HW, there was some testing done on the Japanese side of things that heavily suggested that Fuma is better than Raiton so long as 1) Dancing Edge/Storm's Eye is up and 2) Foe Requiem is not up, regardless of Mudra lag. Given the influx of Skill Speed on our gear at present, I'd be willing to bet that this is still the case, as GCD-clipping becomes more severe the shorter the GCD itself is. If the testing regarding Fuma/Raiton has been disproven, I'm not aware of it.
So generally, you should be able to safely use Fuma unless Dancing Edge is down or Foe Requiem is up, as far as I know.