Ok, I know I said that Discipline was likely in for big changes, but I don't think there's any spec that's more subject to big "this will probably change" caveats than Vengeance Demon Hunters. Why? Well, not only is it a new class (and thus hasn't had at least two expansions' worth of iteration) but it's also not been playable in the Alpha. There is data about the spec, and thus we might be able to glean some sense of what they want the spec to look like, but we should take this with a spoonful of salt.
One thing to notice about the various tank redesigns (and I still need to do Prot Warriors, but their changes look more on the order of Paladin ones than, say, Monk ones - some very notable changes, but not a radical redesign) is that we've seen a move away from high-avoidance. Monks and Druids have both had a lot of focus on avoidance as a means of damage mitigation, and in fairness, it kind of makes sense given the fact that their primary stat (other than stamina) is Agility, which does kind of suggest a dodgy fellow. But Monks are getting more focus on their Brews and Stagger mechanics (which to be fair, is kind of like partially dodging - I interpret it as kind of turning a direct hit into a glancing blow) while Druids are focusing more on Hulking out and just becoming an indestructible bear-monster.
This opens up some design space for a more avoidance-oriented tank spec. Avoidance has always been a little tricky, given that too much focus on it (at the expense of other damage mitigation strategies) can turn a tank's health level into a ping-pong game. Avoidance is fantastic when you have it and utterly worthless when you don't. So any avoidance tank is going to need some way to smooth out the damage they do wind up taking - something that Brewmasters managed with Stagger.
Anyway, what I think this means is that Vengeance might be a bit more avoidance-focused (though given their comfort with iconic Demon Hunter glaives, it might be more parry than dodge,) they'll clearly need some other component to smooth out the damage that they take when they get an unlucky avoidance (or lack thereof) streak.
So let's look at what's currently up. Notably, there are definitely some mechanics that are only half-implemented, including what looks like an entirely separate resource system called Pain. I honestly don't know if this is a secondary resource or something that replaces Fury, so as I said earlier, take this with many grains of salt.
Blade Dance costs 50 Fury and has a 12-second cool down, dealing high damage to all nearby enemies and giving you 100% dodge for 1 second.
Blur has a 1-minute cool down, giving you 50% dodge and allows you to dodge spells and ranged attacks for 3 seconds. Each time you strike an enemy, you refresh the duration, up to a maximum of 10 seconds total duration.
Chaos Nova costs 30 Fury and has a 1-minute cool down, stunning nearby enemies for 5 seconds and dealing moderate Chaos damage to them.
Chaos Strike costs 40 Fury, dealing high Chaos damage to the target. If it crits, it is free.
Consume Magic is a 20-yard interrupt spell on a 20-second cool down. If you successfully interrupt a spell this way, you gain max Fury.
Demon Spikes costs 100 Pain and has 2 Charges on a 15 second recharge. It increases you parry chance by 20% and reduces all physical damage taken by 8% for 6 seconds.
Demon's Bite does moderate physical damage and generates 20-30 Fury.
Demonic Wards is a passive, reducing magical damage taken by 30% and increasing your Stamina by 20%. It also gives you your 6% crit immunity and your 3% lower chance to be parried (standard tank kit.)
Double Jump is the standard Demon Hunter thing, allowing you to jump again when you get to the apex of your jump.
Glide, likewise, after you jump allows you to hit the jump bar a third time to glide down gradually on demonic wings.
Eye Beam costs 50 Fury and is channeled over 2 seconds, dealing high damage to enemies in a line within 20 yards.
Fel Rush has 2 charges on a 10-second recharge, shooting you forward and dealing moderate fire damage to targets in your path.
Fiery Brand has a 45-second cool down and a long range, doing moderate fire damage to the target and reducing the damage the target deals to you by 40% for 10 seconds.
Immolation Aura has a 10-second cool down, dealing a burst of moderate fire damage to all targets around you and then pulsing additional light damage over 6 seconds.
Infernal Strike has a 30-yard range, 2 charges and a 15-second recharge. It allows you to jump to a targeted location, dealing light fire damage to all enemies near the landing site.
Mastery: Fel Blood increases the damage reduction of Demon Spikes.
Metamorphosis has a 3-minute cool down, increasing health by 30% and reducing damage taken by 30% for 10 seconds. Also, while in demon-form, Immolation Aura will automatically always be up.
Shattered Souls is a passive, causing enemies that yield experience or honor to drop a soul fragment on the ground where you land a killing blow on them. Collecting this fragment will heal you for 2% (this could be a typo, because I'd think 20% would be more like it) of your maximum health. If the fragment is from a demon, you'll also get 20% increased damage for 15 seconds.
Shear has a 3-second cool down, dealing moderate physical damage to the target and generating a Soul Shard nearby. It also generates 5 Pain.
Sigil of Inquisition has a 1-minute cool down. It allows you to place a sigil at the targeted location that activates after 3 seconds. Enemies within the sigil are drawn to its center and their speed is reduced by 70% for 6 seconds.
Sigil of Persecution works similarly, with a 1-minute CD and activating at the targeted location after 3 seconds. This taunts all targets within the Sigil, forcing them to attack you for 8 seconds.
Sigil of Silence has the same range, cool down, and activation time, but silences the targets within it for 4 seconds.
Soul Cleave costs 400 Pain and deals moderate physical damage to all targets in front of you and also heals you for 10% of your maximum health. It also consumes all Soul Shards within 30 yards, healing you for 2% of your max health (ok, maybe it wasn't a typo) for each shard consumed.
Spectral Sight has a 30-second cool down, allowing you to see Stealthed and Invisible things and also allowing you to see creatures and treasures through walls for 10 seconds, or until you attack or take damage.
There are two versions of Throw Glaive here, but I think the Vengeance one will have no cool down, dealing light damage to up to three targets.
Torment is your standard taunt, forcing the target to attack you for 3 seconds.
Vengeful Retreat has a 25-second cool down, causing you to leap backward, dealing moderate damage to nearby targets and slowing them by 70% for 3 seconds.
Felblade has a 6-second cool down, dealing high fire damage to the target and spawning 3 nearby Soul Fragments.
So as you can see, this is pretty incomplete. I've added in a lot of the utility spells here because I want to give a full picture of what you're working with. What I suspect is that a lot of the spells on this list are actually Havoc-only, but because that's the baseline spec and the only thing that's been playable, it's kind of left in (it's the same reason we have two Throw Glaives - I'm sure that one is the Havoc version.)
I'd suspect that Demon Spikes will be your main active mitigation ability. Metamorphosis looks pretty believable as a major tank cool down. Demon Spikes manages to get that avoidance theme while using the flat damage reduction as a way to smooth it out. And Felblade, Shear, and Soul Cleave all make the Shattered Souls passive (which exists in Havoc as just a standard "heal yourself up while soloing" mechanic) into a fairly major self-healing theme.
The really big question I have is what form Pain will take. We see things like Shear generating 5 Pain, but Soul Cleave costing 400, which means that unless there's some passive (like generating Pain as you take damage,) that's going to be a whole lot of Shears before you can use Soul Cleave. (Though even if it's only really 40, that's still 8 Shears.)
So while I've been wanting to figure this out for a while, I really don't think we have enough information to figure out exactly how the spec's going to work. I think it's likely we'll see some of this survive. Shear was an iconic ability (at least for tanks) that Illidan had, so I'd like to see some reference to it within the DH arsenal. I think names for standard stuff like Torment will probably be unchanged. And the mechanics of the Sigil spells are cool and unique, so I wouldn't be surprised to see them survive to live.
But the actual rotation and mitigation mechanics will definitely need some work. We don't even really know whether Vengeance will use Fury as a resource, so it's hard if not impossible to really get a sense of the spec's flow.
I do think that with things like Infernal Strike and potentially retaining Fel Rush, we're going to see an even more mobile tank than Warriors or Monks. Guess whose job it's going to be to pick up streaming adds?! So far it looks like flat mitigation, avoidance, and self-healing area all going to be potentially big survival themes. Immolation Aura and Throw Glaive should help for rounding up packs, so while the actual rotation is a cluttered mess, assuming we get abilities that look similar to what we have here, Vengeance should have the tools it needs to keep things running pretty well.
Expect to see another article - maybe an official break-down - once the next build comes out in January.