Diablo III- Skills Article CVII: Witch Doctor, Terror Skills- Soul Harvest

Soul Harvest (59 Mana, Cooldown 15 Seconds): For each enemy up to the fifth within roughly 16 yards, you gain a bonus to your Intelligence based on your level (130 for level 60) that lasts for 30 seconds.

While the uses of this skill aren’t obvious, it can make a pretty hefty difference in your damage swings while it’s active.  The difficulty here is in getting a decently-sized buff out of it- while the maximum is quite large, it requires being in close proximity to a number of enemies, which really isn’t a wise move for a Witch Doctor.  On the other hand, this skill can make it worthwhile to dart into close range and then back out at or near the beginning of combat.  Combined with a hindering effect like Corpse Grasp or Horrify makes this much easier to do, but using such a skill solely for the purpose of enabling Soul Harvest to function with less risk isn’t terribly efficient.  Still, even used only occasionally, Soul Harvest can be a handy boost to your offense and, in a few cases, resistances.

Swallow Your Soul(59 Mana, Cooldown 15 Seconds): For each enemy up to the fifth within roughly 16 yards, you gain a bonus to your Intelligence based on your level (130 for level 60) that lasts for 30 seconds, and regain 39 Mana.

This alteration to Soul Harvest makes it much nicer as a mid-battle buff- otherwise, you’re unlikely to do more than just refund yourself roughly the mana you spent- either because many of the enemies are already dead or because you haven’t spent enough mana to benefit from the maximum 196 Mana restored.  That said, it can be easier to pull off a Soul Harvest mid-battle, but that makes the buff effect a lot less worthwhile, since you’re skipping the opportunity to get it initially.  While the mana boost can be kind of neat, overall this rune isn’t as good as it could be.

Siphon (59 Mana, Cooldown 15 Seconds): For each enemy up to the fifth within roughly 16 yards, you gain a bonus to your Intelligence based on your level (130 for level 60) that lasts for 30 seconds and a set amount of life based on your level (2171 for level 60).

Unlike several of the other healing skills for the Witch Doctor, Siphon can scale fairly well until you start improving on your level 60 gear.  Unfortunately, that doesn’t do a whole lot about the overall useability of the buff.  While the healing can mitigate damage you take for diving into close range to a certain point, actually using the skill remains a risky or even downright complicated maneuver that you really shouldn’t have the time for mid-battle anyways.  Still, this has several legs and an arm up on the previous rune as far as actual usefulness goes.

Languish (59 Mana, Cooldown 15 Seconds): For each enemy up to the fifth within roughly 16 yards, you gain a bonus to your Intelligence based on your level (130 for level 60) that lasts for 30 seconds.  Each enemy counted by this effect has its movement Slowed by 60% for 3 seconds.

This would be a very useful way to keep the mobs you jumped into from tearing you apart while you’re triggering Soul Harvest- if not for the fact that Languish doesn’t affect enemies not counted by the Harvest.  This means that if more than five enemies are in range of the effect, only five of them will be Slowed.  Since you’ll usually be using Soul Harvest either with too few enemies to be as effective as you want it, or with too many enemies for you to benefit from all of, this means that about half the time you’ll still be getting jumped by a bunch of close-range attackers.  So it’s useful, but only to a point.  You’re better off leaning on something more reliable for getting back out of the way.

Soul to Waste (59 Mana, Cooldown 15 Seconds): For each enemy up to the fifth within roughly 16 yards, you gain a bonus to your Intelligence based on your level (130 for level 60) that lasts for 60 seconds.

One of the two most useful runes for Soul Harvest, Soul to Waste makes sure that you dive into close range a lot less frequently, maintaining the buff for a doubled duration that is actually really handy.  This is the rune that really makes Soul Harvest worth regular use.  You still have to worry about accidentally suiciding when you trigger the skill, but at least that worry comes up half as often as it would.

Vengeful Spirit (59 Mana, Cooldown 15 Seconds): For each enemy up to the fifth within roughly 16 yards, you gain a bonus to your Intelligence based on your level (130 for level 60) that lasts for 30 seconds, and every enemy counted takes 70% weapon damage as Physical damage.

If this effect were ‘all enemies in the area of effect’ on the damage, it would be well worth using.  Sadly, it isn’t- it only damages the up-to-five enemies counted off by the skill in the process of setting the buff level.  This keeps it from being a good way to protect yourself from anything that gets too close, and while the damage isn’t terrible, it’s nothing you’re really interested in on a 15-second timer.  Stick with Soul To Waste or possibly Siphon or Swallow Your Soul.