For moogle and kreallana...
Armor is based on who is doing the hitting.
If you are hitting a boss, you are a level 70.
If the boss is hitting you, boss is level 73.
Also there is a blue post that is well summarized by a post by kalgan in my protection warrior thread. You can search for kalgan in the OP of that thread to see precise values for armor reduction already worked out. This thread has a nice summary of that - but the value of armor penetration is fairly straightforward.