Vengeance: Your maximum Hatred is increased by 25. Whenever you are healed by a Health Globe, you regain 20 Hatred and 2 Discipline.
The secondary effect of Vengeance is not terribly reliable- what’s going to interest you is the higher maximum Hatred pool size. Demon Hunters of the control or damage-dealing types are especially going to like this skill, since both of them like dishing out a large pool of either control effects or raw damage all of a sudden by emptying out their Hatred in a short burst before recharging it fully. Even evasive Demon Hunters will like this, if they find they can spare the skill slot- more Hatred is always fine by a Demon Hunter.
Steady Aim: If there are no enemies within 10 yards, your damage is increased by 20%.
An almost purely evasion skill. A lot of battlefield-control Demon Hunters will want to stick near enemies to more frequently and easily apply their control effects, and damage-centric Demon Hunters are in and out of close range far too often to rely on the damage boost. They might still take it, but nobody’s going to abuse this one like an evasive Demon Hunter, who always has a way to get to the far side of the screen from their enemies and still shoot them full of fletching.
Cull the Weak: Damage you deal to Slowed enemies is increased by 25%.
This skill is the control mirror to Steady Aim. Slowing enemies with a Demon Hunter is pretty easy, and this kind of improved damage is incredibly tasty- so don’t skip this if you lay out the Slows. Evasive Demon Hunters won’t be pushing the slows enough to really use this, but some balanced Demon Hunters will have an array of slows at their hands that can really help them take advantage of the opportunity this skill provides.
As a side note to Steady Aim and Cull the Weak, it takes a particular sort of playstyle to pull it off, but it’s possible to put together a battlefield-control Demon Hunter or a mixed control-evasion Demon Hunter who can use both of these skills to their full extent. It’s a bit pricey in that it fills two passive slots and leaves you with a very hard choice for what to do to enhance your side-effects, but it can be done and let you dish out staggering damage.
Night Stalker: When you score a critical hit, you regain 1 Discipline.
Crit-fishing is mostly the domain of two-weapon damage Demon Hunters, who frequently blow through Discipline fairly hard and critical frequently enough to benefit from the passive’s effect. Most other Hunters won’t have the slot to spare for this- focus will benefit them more. If you use Discipline a lot and don’t have a preference for your third slot, though, this can be a decent choice.