Understanding Runes and Stacking.
You seem to be mistaken about something.
The chill effect on the Superior Rune of the Reaper requires having 6 Superior Rune of the Reaper equipped which means 1 in each piece of armor. That would not leave you with any room to use any other runes.
You can see on the runes (0/6) ex : Rune of the Reaper
(1): +25 Power
(2): +35 Toughness
(3): +50 Power
(4): +65 Toughness
(5): +100 Power
(6): When executing a shout skill, chill nearby enemies for 1 second (360 radius).
It means you need each of your armor (6 pieces in total) to equipped 1 Rune each to reach the 6th “(6): When executing a shout skill, chill nearby enemies for 1 second (360 radius).”
So the stacking u saying is not possible afaik , correct me if im wrong.
1 set of armor = need 6 runes
I am so glad I asked. I didn’t realize that the numbers on the runes went with the number of them that you needed.