Actually, the classification of Warrior is a function of what area (Strength, Skill, Will) in which you accrue the most experience (in this case, Strength) and where you spend the most experience points in leveling up (in this case, Physique).
Ganthan's
Class Title Challenge post explains the concept quite well (though I think Notti posted the original research).
I recently completed a game as a Sorcerer, which is challenging because Toughness maxes out with relatively few experience points.