In D&D 4e, defensive skills are supposed to use the better of the two abilities assigned to it: best of strength or constitution modifiers for fortitude, of dexterity or intelligence for reflex, and best of wisdom or charisma for will. Also, the ability that is added to AC is either the better of dexterity or intelligence if you're wearing light armor, or none if its heavy armor. Currently it seems to do this for fortitude alone, but reflex and will do not adjust to take the better of their respecitve skills. As an example, I've included a screenshot of the character I was building, and highlighted Reflex as the example, to show how its using the modifier for Dex rather than Intelligence.
