Reflective scale has a global CD and you can reflect maximum 4 projectiles in 4 seconds. It doesnt matter how many times you casted the skill in these 4 seconds.
In the attachment you can find the proof. I casted reflective scale at 13.5 s, I reflected 2 projectiles at 14.8, then i casted the skill again at 15.3 and reflected 2 more projectiles at 15.4 and 16 then at 16.3 and 16.5 the projectiles hit me.
@ZOS_GinaBruno @ZOS_RichLambert @Wrobel