I agree that eventually your defense skill will catch up, BUT at later levels when it has fallen behind and you're participating in groups with real tanks or start kiting everything, you will rarely be getting attacked directly. Therefore, it will be harder and harder as you advance to get your defense to budge. The only thing that keeps you from being hit is defense. AC reduces the damage from attacks and agility only helps increase defense skill and make dodge, parry, and riposte skills work. When you hit level 40 and your defense is still struggling up, you'll be getting whacked for around a 100 points a shot, and probably getting smacked every hit. At level 20, I had my defense up to 90, even after being PL'd from 14-17