Trinkets
All HFC trinkets are nerfed.
New values for MWF Tome of Shifting Words is 30% for Arcane, 78% for Fire and 68% for Frost. Mythic dungeon trinket and crafted trinkets appear unaffected by said nerf, though there have been changes made. Tharbek's Lucky Pebble, for example, has gone from spirit to versatility.
Doom Nova from Prophecy of Fear no longer scales with Mana Adept (Arcane mastery) and as such is heavily nerfed, the damage now matches the tooltip. It remains 0.9RPPM for Arcane unless the tooltip is lying.
The following test is done with identical gear.
Doom Nova damage as Frost with a 740 Prophecy of Fear: 7500-7501 hits and 15000-15001 crits
Doom Nova damage as Arcane with a 740 Prophecy of Fear: 7500-7501 hits and 15000-15001 crits
As Desecrated Shadowmoon Insignia already was close to Prophecy of Fear on single target in 6.2 this surely causes it to be significantly superior.
Legendary rings
Some rings such as Nithramus have a "$<WarlordsTrinketNerf>*$m1/100$%" in place of the 44% number on the initial damage increase, as seen here:
Maalus and Thorasus look as they do on live, not having the WarlordsTrinketNerf part of the tooltip but rather the expected 44% number.
Gems
Epic gems now provide 200 of a chosen secondary stat, up from 75. As such, having a socket is significantly more powerful than having a WF piece, except in the case of your weapon. (And potentially some class trinkets)
Blue gems provide 160 up from 50.
Tier sets
Pre-WoD set bonuses are now disabled. No more prepull shenanigans.
Enchants
Values remain the same for "Mark of", "Gift of" and "Breath of" enchants.
Multistrike is gone
Spoiler tag might not entirely be true, as Chill666 points out, Demonbuckle Sash of Argus went from Mastery + Multistrike to Mastery + Haste. (I haven't verified personally)
Multistrike gems have been changed to haste.
Mark of the Frostwolf retains its mechanic of being able to stack to 2, but now provides critical strike instead of multistrike.