Stacking buffs

Im putting out a request for the folks that have tons of time on thier hands to do some looking into how buffs and debuffs that deal with damage reduction in this game work together.

For instance, Putting rampart up gives a 20% dmg reduction buff, if I stack foresight on top of it for another 20% dmg reduction buff, are the two buff stacked together before calculation for a 40% buff, or does one calculate before the other resulting in only a 36% buff

Or what about buffs and debuffs, will eye for an eye (after the enemy suffers the debuff, not just having the buff on th tank) stack with rampart

Also what about other forms of debuffs such as the rage of halone strength debuff + virus, which affect stat values and not outgoing damage

TO anyone that has the time to work through these things, I salute you

Rampart and Foresight have a different function.
Foresight will increase your DEFENSE by 20%.
Rampart provides damage reduction of 20%.

From what Kitru states all of the buffs/debuffs are multiplicatve, but ive yet to verify it.

Foresight is ~5% if you're lucky.

You mean if you have the gear for it.
I mean EVENTUALLY abilities like Berserk/Foresight would be better than their counterparts in THEORY.

I stand corrected, I would still like to know the answer to this, wont really change how I use them much but will change how I think about them