Update: there is new information on how World Bosses will work at the bottom of the blue post compilation.
We have more details on the Season 4 raid loot changes, from clarification on currency acquisition, to tier set availability, Shards of Domination being disabled, how LFR and open world loot sources will work and more! 

Season 4 (Source)

Hey folks, will get to some responses soon but I’ve edited the main body to reflect something that was missing, which is to say:

Unique means killing the same boss during that same week won’t give credit – killing the Tarragrue on Normal and Heroic in the same week will only give 1 kill. This means the soonest a player could get all 3 Dinars is week 6 at the earliest, not weeks 1-3 as some have speculated. Sorry for the confusion!
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Dropping in to clarify a few common trends of questions I’ve seen around, then will get back to combing. I want to keep my responses to things related to the Raid rewards as outlined in the post:

What about Tier Sets?

Your 9.2 Tier Sets are still active in Season 4, and the Creation Catalyst will remain on with all of its accumulated charges. Tier Tokens won’t be added to Castle Nathria and Sanctum of Domination, as you’ll be able to upgrade any item you get to a higher ilvl piece of Tier just like you can on live right now.

Domination Sockets

Shards and Domination bonuses will be disabled entirely for Season 4. We didn’t want to place extra pressure on the tuning of specifically Fated Sanctum to require it, and there was enough of a class/armor type disparity at which specs/classes could potentially wear a 3-set Domination Bonus and their 4-piece vs others that it would create a weird imbalance on those weeks. We’ve also heard from player feedback that it would feel unfair for players who didn’t hold onto Domination Gear to be at such a disadvantage.

LFR/Outdoor

Looking for Raid will have a Season 4/Fated Difficulty, and all wings will be available at the start. This is to say if the rotation begins with Castle Nathria being the Fated raid on rotation, all of LFR Nathria will be replaced with Fated LFR Nathria, at higher item levels. LFR also counts for quest progress, so players who don’t full clear a raid for the week can collect what leftover bosses they need from there.

Additionally, the World Boss related to whichever raid is currently Fated will also be scaled up – more difficult, and dropping ilvl 285 Fated gear.

Why only Weapons/Trinkets?

As others in this thread have mentioned, neither of these systems are intended to replace the primary method by which players acquire gear – having all of an expansion’s raids be at current item level is something entirely new to WoW, and will create both a lot of powerful combinations of items, as well as a lot of frustration at not receiving them. We wanted the Vendors to be targeted at the pieces of loot we’d already seen are most impactful to a player such as to create an intense negative reaction when situations arise like the post mentions. Many players feel if they can’t get an Edge of Night, they can’t play Rogue in 9.1/9.2. Rarely do players feel they can’t play because they are missing boots or bracers. Focusing in on these higher-tier items keeps these vendors special, and the system focused on that protection, rather than being an alternative/replacement gearing method (which it is not).

Great Vault integration?

A common idea so far is if the Great Vault tokens could integrate some of these. While we’re not interested so far in extending the amount of Dinars a player can get in the season, offering some of the heroic or mythic upgrade shards in some form could absolutely be possible, though we’d still want to make certain you can only purchase Heroic or Mythic upgrade shards if you’re actually raiding some amount on those difficulties. Not a guarantee, but not an impossibility.

Oh, I forgot one –

Heroic & Mythic Upgrade shards

these don’t upgrade in a linear fashion. this is to say, if you have a Heroic upgrade item, it will take an LFR or Normal item, and make it into Heroic. Similarly, if you have a Mythic Upgrade Item, you can target LFR, Normal OR Heroic, and it’ll transform into Mythic. They don’t have to be in sequence – so primary Mythic raiders can choose to ignore Heroic if they desire.

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Whichever boss (Valinor, Mortanis, Oranomonos, and Nurgash) is naturally up on a Fated Nathria week will be boosted. They’re all considered the Fated World Boss with regards to the fact that they were designed as companions to the raid Castle Nathria (though Nurgash is absolutely closer to home!)