Basically we took damage samples in arena and catacombs using an armor with 1-4 defense in magical and physical. The characters base dexterity was 100 for all the tests. We took over 2000 samples for levels 45, 55 , 65.
J_B and I then did a spreadsheet that calculated your average damage taken based on your level, amount of vit/int, type of armor, amount of EE on that said armor. However the link for spreadsheet wasn't approved so I can't hand that out.
These are some graphics I made that illustrate quite well the relation between all these stats. If anyone has a more specific question I can probably answer it.
As far as leather armors go vs scale armors, they will give extremely similar results. They both have that same base defense, which is what your looking at. The scales will have a higher max defense of 12 (at tier 14) for physical defense and a lower one of 12 for magical defense. However this is quite irrelevant since the higher tier values aren't utilized at their full potential anyways. They will just give you a slightly higher % chance of getting a higher roll on the defense.
In higher amounts of EE (180+) scales and leathers will work practically exactly the same.
I also have similar conclusion for lower tiers however the conclusions will be the same so I didn't make any graphics. Their mostly for specific examples, if I ever want to calculate exact numbers.
Enjoy!