Look,This is the FAQ given by DiabloMonkey/Ben Blank, which provided us with more details about Dodge and Block.
Q：How do armor, resistances and missile/melee damage reduction interact?
To clarrify, say I have 20% block and 16.7% dodge, does that add up to 36.7% of what I guess would be called "absorbing" damage?
A：The short answer, No. The long answer, Yes.
In your mind you should classify Armor and Resists as Damage Reduction. Block is a different kind of damage reduction and its value scales.
Dodge is not Damage reduction, but rather... Damage mitigation. I will try to explain below with an example. http://d3.gameguyz.com/node/2512.html