How does mitigation stack in FFXIV?

[Sleigh]

By this I mean, how do CDs multiply or add or subtract with each other to determine your damage? For instance, PLD with Shield Oath:

20% DR. Takes 80% damage by default. Now add Rampart, which is also 20% ... does this in turn make PLD have 40% DR, or something more complicated like .8 X .8 = 64% damage taken AKA 36% DR?

[Squrilruler]

Mitigation is multiplicative. Here is a reddit post about it:

http://www.reddit.com/r/ffxiv/commen...licative_what/

[TouchandFeel]

It's multiplicative as was stated above, meaning that the second example you gave is correct, where Rampart being used while in Shield Oath would do 20% damage reduction based on the 80% damage being taken due to ShO, resulting in (80x0.2)+20=36% damage reduction.

A little annoying that because PLD's tank stance mitigation is % damage reduction based, it reduces the effectiveness of the job's main defensive CD's, Rampart and Sentinel.

[Sleigh]

Thanks for the link and info.