Not sure if this is a bug or I'm wrong, but I tried to cast a Ghostly Visage Spell from a scrolls with my bard and got Arcane Spell Failure.
I'f I'm not wrong, since it is a Bard spell, the spell should have an automatic success (it seemed to have) and not be subjected to arcane spell failure, since I was using Light Armor.
If needed, I may try to recreate it. Not wishing to waste more scrolls before that, however.