Here's something to think about.
Why is the Justicar the only class that can use a heavy shield? Also, says it's heavier but I don't notice a change in speed to attack or defense. Please correct me if I'm wrong as the Justi is not my forte.
Shield of void (top tier light shield)
540 defense
12% block chance
50% block mitigation
Wall of Iron (top tier heavy shield)
782 defense
24% block chance
50% block mitigation.
So 1 hand Justies with heavy shield seem to have an advantage in the defense dept.