According to wowwiki for chars level 1-34 you gain base/2 .. so 16 def rating will be 8 def skill which will be 8*0.04 = 0.32% miss, dodge, parry and block. So about ~1% total avoidance and subject to DR
+6 to stats will give you 1.176% dodge, 12 armour, more health, more crit, etc, etc