I don't think Strength effects ranged attacks, does it? Augment Damage does not.
If you save before fighting a group of monsters, you can kill them and keep track of the damage, then use
iZakaroN's SaveEditor to remove (perhaps in a copy of the game) one or more points from Crossbow Expertise and kill them again. Comparing average damage at different skill levels (ie 0 and 5) with the exact same equipment and opponents should reveal if the skill works or not.
