After spending some time reading this thread, I feel I must point out 3 things.
1. This graph is outdated, however the formulas that the graph were from have been updated and are here
. Justcae does however make a point that there are diminishing returns. For example, from some number crunching I did, at around 360 absorption rating for every 1 more absorption you get you get +0.05% absorption (it drops even more as you go higher).
3) Shield and Absorb relate to one another on a 1 : 1 basis. If you have 25% Shield, and 50% absorb, and are attacked 100 x's for 100 damage you can expect to absorb 1250 damage. If you have 50% Shield and 25% absorb with the same parameters you can expect to absorb 1250 damage. They relate directly with one another. Hooray!
2. This needs some qualifiers. Justcae you are correct that 25% shield and 50% absorb produces the same results as 50% shield and 25% absorb. However 20% shield and 55% absorb does not produce the same results as 25% and 50% absorb. I don't know if that's what you meant by a 1 : 1 relationship, I may be interpreting that incorrectly. However it is true that for all values of shield and absorb that if you interpose them you get the same results. ie. 10% shield 50% absorb is the same as having 50% shield and 10% absorb.
15% Defense, and 60% shield does not mean that you will mitigate 75% of attacks. Instead it means you will mitigate 15% + (60% * .85) = 66% of all ranged/melee attacks.
15%, 60%, 60%
1) 15% chance 100% damage
2) .85 * .6 = 51% chance 60% damage
15% + (51% * 60%) = 45.6% of damage mitigated
3. The above statements are talking about 2 different properties.
The first one by JustCae is refers to the number of incoming attacks. It means that 66% of incoming energy or kinetic attacks will result in you dodging or your shield activating.
The second statement by MattFrontino refers to the amount of damage actually mitigated by your shield absorbing damage, or you dodging it. The other thing I feel is somewhat pertinent is that the math in both cases is correct.
So having 15% dodge, 60% shield and 60% absorb will result in 66% of kinetic/energy attacks being dodged or absorbed and have 45.6% of the damage from kinetic/energy attacks being mitigated from either dodge or absorbtion.
However that being said I'm not very familiar with what is/isn't possible so I don't know if 15% dodge, 60% shield, and 60% absorb is possible.