Haunt: Poisoned Spirit
Poisoned Spirit will give you 20% increased damage against effected enemies. Another option would be Resentful Spirits to cast 2 Haunts at once(3 if you are wearing the Haunting Girdle.) I think both options are good and it's really up to personal preference.
Locust Swarm: Pestilence
Pestilence will allow Locust Swarm to spread very quickly, the current set up I've been running has The Furnace in the cube, but a more lazy version of the build runs Wormwood in the cube to cast Locust Swarm passively. Also, if you decide to run Vile Hive, this automatically gives you the Pestilence rune. If you decide to run Wormwood in the cube, its also an option to just drop Locust swarm from your skill bar completely and have the Womwood cast an un-runed version of the ability. If you do this, I would recommend running Zombie Dogs: Leeching Beasts on your bar for more sustain.
Soul Harvest has a very small radius, so grouping mobs very closely together with Piranhado is key to completing high level Greater Rifts quickly. This will also help you maximize your Area Damage.
Spirit Walk: Jaunt/Severance
Jade Harvester is a pretty squishy build, so I prefer the 3 seconds of invulnerability from Jaunt. Severance will allow you to move from pack to pack much quicker with the 100% increased movement speed. I think this is again, up to personal preference.
You get every rune of Soul Harvest with Jade Harvester, so it really does not matter what rune you run on your bar.
Horrify: Frightening Aspect
Horrify will give you a bit of Crowd Control but this is really there for the increase to Armor. Again, this is a squishy build, so you really need to maximize your toughness wherever you can.
- PASSIVES -
Creeping Death reads that your Haunt and Locust swarm last almost forever, which is actually 3600 seconds or 1 hour. Your Soul Harvest will then consume 300 seconds worth of your DoT's.
Cooldown Reduction is one one of the most important stats in any Jade Harvester build. Grave Injustice will allow you to Soul Harvest much more often as well as group mobs more often with Piranhado. This also allows you to keep the armor buff from Frightening Aspect up much more often.
You'll always be within 20 yards when you Soul Harvest Making Confidence Ritual one of the best damage buffs for the build.
Spirit Vessel for a second life. It's possible to fish for a really great rift and drop Spirit Vessel completely, but again with how squishy the build is, I would not recommend it.