Ippokrates wrote: »Last time I checked damage reduction on my Templar High Elf, there is kind of multliplicative reduction. Minor Protection is giving 5% reduction, race ability also 5%, but both gave only 9% reduction, not 10.
Similar thing i have noticed on cost reduction - for every additional reduction from skills, equipment, etc. racial passives for Redguard and Imperial were giving less and less - usually 1%
I expect there is not a cap but I expect some types of damage reduction are less effective when stacked with other damage recutions. Meaning the armor resistance reduces damage by X, but that is the damage that actually hits it so the protections buffs make armor less effective.
The major protection buff should enter the equation first so the armor mitigation comes in after the protection buff does its work. That means an attack of 10k is reduced to 7k after major protection which then becomes 3.5k after armor resistance comes into play (assuming 50% resistance. I am just tossing numbers out and simplifying things.
So there is a lot that can become stacked but I doubt one can reach 100% damage reduction.
In PvE, very much so for a tank. In PvP, I expect there are many tank builds that stack a lot of damage reduction. .