I’ve been running Signet of Agony since level one due to it enabling my curse damage/crit build. While I do appear to be gaining some sort of armor after striking things cursed by it, due to a lack of an icon I cannot say for sure whether it’s proccing Bone Armor properly.
Additionally, the curse does not appear to be slowing any enemies. Does Signet of Agony disable on-cast effects like Mark of Death from Signet of Mortality and Chill from Chillblains? I remember reading somewhere that the devs try to limit too many icons on the screen and thus only have them triggered for more noteworthy effects.
I don’t wish to remove the point to test this theory out myself.