Cooldown reduction affects the maximum cooldown timer, not the remaining time.
If you have 5 pieces of gear with 2% global cooldown reduction, it’ll total up and apply a 10% reduction to the base cooldown of an ability.
Likewise, perks that reduce active cooldowns by a percentage work of the base cooldown.
In fact, dunno if it’s a bug but any perk that says “reduces cooldowns by n% on hit” actually means per target hit.
I have a clip of myself instantly refreshing the 45 second cooldown of Defiant Stance with a single Reverse Stab by hitting 4 skeletons at once with it, twice in a row.
Since I am tank too, i know about that and it is not that hard to achieve this in PVE, but in PVP I think its very hard to achive instant cd of Final Stance.
I would be realy mad if they decide it to be a bug an therfore change it.