These are most of the undocumented changes who has been reported in the 7.1 Return to Karazhan patch.
All reports come from this thread on wow subreddit, i put them down here for ease of reading (because dark themes like that one are pretty much unreadable withouth killing your eyes).
- Many are suggesting a noticable increase in legendary drops.
- Companion app has been updated for Artifact Research? (http://i.imgur.com/dFWA6xC.png)
- Glider items that make you go faster no longer work in dungeons.
- You can solo Galakras in SoO now. You're able to shoot two shots with one cannon to take him down.
- Mount drops now get announced to guild chat the same way legendaries do.
- Withered J'im is now on the Unleashed Monstrosities achievement.
- Vault of the Wardens, changed the graphic of Cordana's Deepening Shadows to a dark, purple texture that is harder to see. It also spreads a LOT slower.
- Dalaran Hearthstone now sorts along with other hearthstones
- The legendary Sephuz's Secret has been nerfed. Silences no longer proc it, and CC abilities that also deal damage will no longer proc it on bosses.
- You can now ask Dalaran guards for directions to the transmog location.
- Some new server connections have been put in place.
- You can right click followers to add them to a mission now.
- Mana-tinged packs now drop items that you can use to create mana instead of dropping raw mana.
- Flight map flight path icons have a darker border around them.
- In Suramar commons areas, detection circle graphic and actual detection range now match.
- Pressing "Z" or your sheath/unsheath hotkey may crash the client
- If it doesn't crash yours, you can sheathe/unsheathe weapons in the preview window using you key bind.
- The top line in a chat box now partially shows instead of just being blank
- There is a new "Request to Join Group" button when right-clicking players in a group.
- Action Cam can be enabled again
- Target Scan is broken. Target Nearest Enemy still works.
- Water on the minimap has been updated in many areas
- Flight Whistle now triggers as a cinematic.
- The Broken Isles loading screen is different now. Varian has two red swords now instead of a blue and a red sword.
- When viewing loot in the dungeon journal, you can now filter by what slot it fits.
Transmog / Appearance
- Players can now hide their belt at the Transmogrificaction NPCs!
- Some weapons that disappeared when sheathing are now appearing.
- Weapon positioning on fist weapons have been improved.
- You can now use channeled artifact power items while moving.
- Stealth is now easier to detect. Possibly unintentional, recommend submitting bug report.
- Many recipes no longer have reputation requirements
- Crafted equipment that is upgraded with obliterum now goes up to 8 instead of 7
- Crystal Vials from vendors now come as 20 in a stack as opposed to 5.
- Starlight Rose Dust was upgraded to a common quality item
- Cut gems can no longer be put in the reagent bank.
- There was a bug wherein Disturbed Podlings (chance to spawn when herbing in Draenor) did not drop loot for level 101+ characters. No more! It's been fixed.
- Glyph of the Blazing Savior works now.
- Underlight Angler (fishing artifact) trait "Way of the Flounder" now persists after you click your bobber.
- Excess ancient mana is now ignored on mobs and nodes. Allows skinning with mana on corpse.
- Active quests number tracker is back.
- At the end of your class campaign you only need to complete 20 world quest now instead of 30
- Rep gains for feeding the addicts in Shal'Aran now up to 75 from 50.
- Arcane sentries and mobs that can be activated/given ancient mana have had their costs reduced. The text does not reflect this, but it is shown in the confirmation window when you set it up.
- Selecting the emissary mission icon on the map changes the map to that zone.
- Class hall upgrade that completes a WQ no longer counts toward emissary quests.
- Travel form is now the same speed as a mount. Cenarion Ward now removes shapeshift forms.
- Druid bat form once again makes bat noises.
- Druid order hall set is now a dress instead of chest + legs.
- Wraith Walk now usable when dead.
- Sludge Belcher no longer turns into Rotface/Festergut model.
- Now has Earthbind totem.
- Glyph of the Spectral Raptor now uses the newer raptor model
- There's now a proc icon when Holy Fire resets
- Shadow form no longer affects mounts
- The Silver Hand artifact has had a cosmetic change. The libram you get that straps to your side now won't be covered by big belts that have dangly bits.
- Aimed shot for MM Hunters nerfed ~5%
- Can't use Essence Swapper to turn Hati into a Valkyr any more.
- Crippling Poison no longer applies to bosses in dungeons.
- Many teleport spells now have unique art
- Artifact fireballs now change slightly based on artifact appearance.
- Fire Mages can now turn off the flame orb effect of Felo'melorn by talking to Archmage Melis
- The travel time upon cast and activation time on Demonic Gateway has been significantly sped up.
- Lowered the cap to 109 on 'Enslave Demon' down from 110
- Glyph of Voidlord has a new model which looks like a voidwalker wearing armor, instead of the electricity looking one.
- Contagion is now 12%; was 15%.
- "Glyph of the blazing savior" is no longer bugged and can be inscribed on intercept for protection spec.
- A lot of changes were made to pvp talents. You should open yours and review them all again.
- Warden towers were hot-fixed to give 300 honor again, and apparently the "other" pvp world quests (like the darkbrul arena) now reward 500 honor.
- Halloween Broom is no longer usable in rated BGs
- Battle Standards (both guild rep/honor bonus and the health increase one) are disabled in battlegrounds.
- Engineering items such as nitro boosts and the built in cloak glider, which were previously disabled in battlegrounds now function.
- Can no longer use flasks or gain benefits from food in random bgs.
- The sting pvp talent rows was changed New talent "Trailblazer" is 5% stronger than the notes say
- Counteract magic used to heal for 150% extra when the target was afflicted by a magic dot, now it's 125%
- Zen focus (Honor talent) empowered the Thunder focus tea (which could be reseted with Rising thunder)... now it is another skill, "Zen focus tea"
- Surge of Mist is now on an 8 seconds cooldown, it was 6. (thanks to Specificscientific) This means that we can no longer reset the immunity to silences and interrupts.
- Casting Circle talent no longer grants immunity to silence/interrupt while you stand in it. It now reduces duration of silence/interrupt by 70%