Condition Duration Nightmare Rune
I came to post something similar to this. On my thief, I have 10% duration from traits, 10% bleed duration from agony sigil, and 15% bleed duration from Rune of the Krait. My condition duration on the hero panel states 20%. If I unequip my weapon it drops to 10%. Equipping or unequiping my armor pieces does nothing. So it appears that I’m getting no duration stat from my Krait runes, similar to your nightmare runes. Hopefully, this is just a display problem. It’s just odd to me that the bleed duration from the weapon sigil works, yet the duration from the armor runes does not.
It is just a display issue. Same issue with the Lich runes. You can verify this by turning off your auto-attack, and using just BiP on a target and looking immediately at the number of seconds the bleed has left on it.
I have the same issue with superior rune of the nightmare.
I have a Necromancer and when I take food with condition duration then I can see the difference in the stats and also the time on the conditions is longer but when I take off my armor with this runes (5/6) then nothing happens, the condition time does not change.