Not sure if anyone can confirm this, but for my runs so far, the consume portion of damage from Jade Harvester is not doing any damage to monsters.
Thanks!
Are you using the Creeping Death passive?
If no, that’s why. You need that passive in order to extend the duration so that you actually have enough duration to consume. The 2p bonus doesn’t work off consumed duration, it just deals damage, so that’s why the 2p bonus will work without Creeping Death. But for the 6p bonus to deal big damage, you need the passive.
Was about to post an update but got caught up in life.
After around 45 minutes of me posting this, with no changes to my character, it started working again. Not sure what the issue was, but thanks for the response 
The property of 6 items partially does not work.
“(6) Set:
Soul Harvest reduces damage taken by 50% for 12 seconds and consumes your damage over time effects on enemies, instantly dealing 10,000 seconds worth of remaining damage.”
I don’t see any damage from using Soul Harvest. The taking damage reduction works correctly after using “Soul Harvest”.
“(2) Set also works correctly:
When Haunt lands on an enemy already affected by Haunt, it instantly deals 3500 seconds worth of Haunt damage.”