Sony has stated on serveral occasions that AC works differently for each class (meaning a Warrior with an AC of 600 gets more protection than a Wizard with an AC of 600).
You might also want to think about having a variable for each class that will "modify" the base variables. For example:
Code:
/* Damage reduction (%) bonus that Warriors get IN ADDITION to base AC damage reduction. */
...
WAR_AC = 10; // takes 10% LESS damage
WIZ_AC = -5; // takes 5% MORE damage