Yep. 7 + user's Attack - foe's Defense. Vamphibians get shut down hard by Defense gear.
Black Knight throws out a Star Burst when his counter is over 40 Starforce, so that's a minimum of 70 damage before Defense with his Attack factored in. His AI is pretty complex, too- it boils down to "Always use Barrier Shift when possible, otherwise try not to get messed up too bad by the current Barrier Shift weakness".
His Block has a long delay to it, but he won't use it if he's weak to Thunder. However, a reward from one of the sidequests can help a lot against his Block.