Damage formula for Barrage skill?

[Donkeyton]

Does anyone know what the precise formula for Barrage is? I assume it has something to do with the X value (ordinarily set to 50 in this case) as a percentage of total attack value. So X=50, in this case, might mean that each hit in the barrage does 50% of the damage of a regular attack (thereby making one Barrage equal to about two hits from a normal attack). This theory seems to hold up in casual observations of Barrage vs. normal attacks vs. Dual Wield. But raising the X value in FFTPatcher does not seem to raise damage, and lowering it does not seem to lower damage.

I know some folks have played around with the Barrage damage (I believe it was reduced to 35% in 1.3?). Can anyone please explain exactly what the formula is, or what the effect of the X value is?