Patch Notes:

Improvements and changes
Improved several journal entries to be clearer to the player if quests get closed automatically
Added several items and related journal updates to improve links between certain NPCs and story lines
Journal update XP gains are now shown alongside the corresponding update
Improved performance in very specific locations, related to items being equipped by players or NPCs
Added “Pick up and send to wares” and “Steal and add to wares” in context menu of world items
Increased prices of unique weapons sold in Arx
Added missing weapon skills to unique two-handed weapons
Flaming Crescendo should now correctly receive bonus damage from Intelligence
Using the Equalise skill is now a hostile action
Skills from items now correctly respect weapon requirements
Reactive shot no longer deals damage on casting
You can now enter Sneak mode after activating the Play Dead skill
Added several new effects to make important dialog moments stand out more
Adjusted Meistr’s Vault so that it gives a ritual dagger and ritual bowl each time the player opens it, if the player does not have it in his inventory
Improved detection for being able to flee from combat
Skill preview trajectory should now be more accurate when fighting certain enemies
Improved landing position of Backlash skill
Blessing an electrified steam cloud now results in a blessed steam cloud
Blood Totem is now immune to Decaying status
Improved AI behavior that was leading to skipped turns incorrectly
Partial Action Points, after moving a small amount, are now saved correctly
Added several new icons
Framed Frost runes and Framed Thunder runes now have the correct bonuses
Fixed several crafting recipes that incorrectly required very specific items or gave incorrect results
Items dragged from equipment slot to inventory are now placed in the correct slot
You can now examine an enemy, even when it is not your turn
Roses increase Wits when consumed
When stealing a container, cost of its contents should be added to the cost of the container
Demonic Tutelage and Flaming Tongues now attack enemies until their duration runs out instead of only attacking first three enemies
Charm is now cleared when the charmer dies
Charm is now cleared from summons when the owner is uncharmed
Updated several skill tooltips to take into account extra modifiers
Updated several audio effects
Temporarily allied NPCs no longer have crime investigation behaviors about the crimes they helped commit
Henchmen now correctly have Source skills depending on where the player is in the storyline
Gratiana now sells back Soul Jars from other NPCs if the player gave them to her
End game Arena combat was made clearer to the player. Arena combatants are now clearly marked and they will target each other first
Updated Empyreo the Stalwart’s stats and abilities
Outlines now include corpses
Added player feedback when being Enwebbed, Crippled, Entangled or Encumbered
Improved Inner Demon, Demonic Tutelage and Terrify visual effects

Thank you for posting the patch notes. Sadly the in-client-window for the patches on Galaxy hasn't been updated in a long time.

No Tarquin fix though? At least not mentioned. Gotta go ingame and check if he's still stuck in the graveyard of act II...
edit: Sigh... not fixed.

OMG they convertet Hanal Lechet into a two handed axe now my prince is weaponless. But they haven't change the stats or attributes for example it still gives +1 single handed

Wow... that's not your regular stupid, that's advanced stupid! :D

Seconded; just downloaded the patch via GOG Galaxy but am now unable to play with a non-galaxy friend.

(Edit: But thank you so much for the changelog :))

http://larian.com/forums/ubbthreads.php?ubb=showflat&Number=633692

Looks like the notes here talk about it? So you are saying the galaxy client knows to download the patch, but it's not listed on the manual download page, right?

Yes.

Still broken though. There are already user comments saying the same. Maybe they meant something other than the anathema quest with "his questline".

This is great. I can't even open inventory now. If I do that it just starts spamming "inventory open" sound constantly.
Some old bugs are still there, despite being in that list above.
And this devs asking "why only 6% of players finished our game?" Why indeed.
Too bad I can't refund now.

You're all very welcome for the patch notes. I have this weird thing about not being able to see patch notes when said patch is made available. So I took it upon myself to post them here. Finally, I've edited my original post due to it being incomplete. It should take effect soon enough. Best, -M.

Bug Fixes
Fixed Tarquin’s location and dialog after finishing his quest line
Fixed sorting by last picked up
Fixed ghosts spawning in incorrect locations
Fixed auras not correctly reapplying under certain conditions
Fixed forced group formation initializing when using certain spells to initiate combat
Fixed a problem with characters not following the party correctly anymore
Fixed Party Follower NPCs possibly getting stuck in dialog when talking to the wrong Player Character
Fixed triggering the unconsciousness of Dallis or Lucian only once if they are lying on a damaging surface
Fixed rested status blocking dialog with Malady at the end of the game
Fixed Kniles not participating in combat if he's teleported into a closed cage
Disabled trading with companions before recruiting them
Fixed Dallis’ moving closet on the Lady Vengeance
Fixed characters not being reassigned to the correct player after loading a co-op game from main menu
Fixed a dialog issue between Fane and Lohse after visiting the Hall of Echoes with Fane. The correct god is now mentioned in the dialog
Fixed several dialog issues related to gender
Fixed several dialog issues that would result in dialog loops or incorrect flags being set
Fixed several XP reward issues related to quests and certain enemies
Fixed the Red Prince being invisible during the wagon scene with the Red Princess
Fixed flaming pig not being blessed or cursed when talking to a shrine for the first time
Fixed a visual issue with electrified surfaces re-appearing after it wears off
Fixed an audio issue during the Council of Seven Arena, when talking to the embodiments of the gods
Fixed the sewer pipe exit to Fort Joy swamps. It can no longer be destroyed
Fixed the Scroll of Atonement disappearing from inventory
Fixed the Cathedral door being blocked in Arx
Fixed characters becoming stuck after summoning a totem in combat and then running out of combat
Fixed being able to save right before entering the magic mirror
Fixed being able to use the magic mirror with party followers by using context menu
Fixed an issue wherein a player joins the host for the first time and is being assigned the main character when host is controlling a companion
Fixed a crash related to dialog flags not being removed properly
Fixed Higba incorrectly being a party member later in the game due to Charmed status
Fixed a crash related to summoning totems near certain objects
Fixed a crash when transitioning to certain regions or instantly reloading the last savegame twice (runtime error)
Fixed wrong spirit appearing after killing Jonathan
Fixed dialog getting stuck when a charmed character enters the dialog
Fixed dialog history not showing up when a client player joins a dialog
Fixed a blocking issue during the Kraken fight when instantly killing Braccus during the first turn
Fixed turn order issue when characters transform (for example: The Doctor)
Fixed several journal updates triggering incorrectly under certain conditions
Fixed a crash when trying to teleport an item that has been picked up by someone else
Fixed several audio issues with the Kraken combat
Fixed several issues related to multiple tutorial messages popping up
Fixed Malady thinking Gareth is missing when he has left the area correctly
Fixed not being able to re-recruit party members on the Lady Vengeance due to a message saying the party is full
Fixed several issues with end game combat when the main character dies, but the player still defeats Braccus
Fixed Magister Borris not dropping Ifan’s contract
Fixed Ifan having Pet Pal talent regardless of which class you want him to be when recruiting him
Fixed Malady’s attitude dropping lower than intended
Fixed Jahan becoming hostile on the Lady Vengeance if the player frees the demons
Fixed tooltip for Evidence Chest
Fixed not being able to deal any damage to a number of specific NPCs
Fixed bears attacking when player uses Source Skills near them

Last Part of Patch Notes:

Fixed not being able to get Infiltration achievement for lockpicking as an undead
Fixed Gareth’s dialog on the Lady Vengeance if he followed the path of light in Reaper’s Coast and spared Alexandar
Fixed several automated dialogs repeating at incorrect times or too frequently
Fixed being able to craft scrolls with important letters, destroying them in the process
Fixed Sallow Man dialog. In certain cases, he would not give out the Capacitor
Fixed Fane incorrectly being placed into a crime dialog after being dismissed
Fixed the Doctor having incorrect stats after transforming
Fixed being able to log in with more than 2 profiles when using controllers
Fixed being able to flee from certain situations when the player is not supposed to
Fixed being able to target corpses correctly when using a controller
Fixed dialog not scrolling anymore after loading while in a dialog
Fixed Avatar character not being assigned to player anymore after specific party death scenario
Fixed alignment issue causing player characters to be neutral after being resurrected
Fixed losing Black Rose status effect during certain story events
Fixed dialog issue with trespassing in Fort Joy near certain Magisters
Fixed Shackles of Pain effect after loading
Fixed Throw Explosive Trap skill in Arena Mode
Fixed barter trader exploit when using a controller
Fixed not being able to disable certain add-ons after campaign creation
Fixed various minor animation issues
Fixed a dialog issue in when fleeing from the fight with Saheila
Fixed Tarquin Skill Book selling issue
Fixed several issues related to destroying Soul Jars
Fixed target picking issues when near Noxious Voidwoken bodies
Fixed an issue with Elemental Affinity not updating the Skillbar correctly in certain cases
Fixed some cases when Blitz Attack and Backlash would ignore Ruptured Tendons
Fixed several map markers
Fixed being able to break the Kraken’s skill “Fate of the Sworn” by spamming ESC as he is casting it
Fixed having a summon time out in the Hall of Echoes resulting in the camera going to an incorrect location
Fixed empty catacombs pipe puzzle in Arx

UI Fixes
Improved tooltips for runes
Minimap now shows the direction of pings from other players when they are out of range
Fixed tooltips for surfaces not being displayed when using a controller
Added extra feedback for controller mode when not being able to pick something up due to not having enough strength
Fixed refresh issue of tooltips when players send items to each other
Character Creation: players can now edit their name while navigating any tab
Assigning points in Constitution in controller mode character screen should not increase Vitality until the point distribution is confirmed by exiting character screen
Fixed Direct Connect option in controller mode
Fixed being able to see target health bars when it is not your turn in controller mode
Updated the Options menu
Added UI fallback font for Chinese characters
Added turn timer in Arena Mode when using a controller
Fixed action bar getting stuck when skill bar is hidden by other interfaces
Incompatible saves now have a version indicator on the load screen
Fixed an issue in Arena Mode where one player would be unable to select heroes
Fixed a blocking issue at the end of the game when you deny Ifan having his revenge

GM Mode
Updated music tab. Added new music and fixed several playback issues
Added support for multi-region levels in GM mode
You can now drag items with or without snapping to terrain (by pressing the Caps Lock button)
Fixed inconsistency when spawning and dragging an existing item
Fix for characters sometimes not being assigned to anyone when a player disconnects from a GM session
Fixed error 300 and error 302 issues and related crash when trying to load zones that had a global entity removed
Fixed not being able to see custom stats tab when playing with controller
Fixed a crash related to NPCs joining dialog
Fixed a crash related to duplicate characters not being cleared correctly
Fixed a crash when dragging certain items to inventory
Fixed AI type panel and Alignment context menu not closing when GM changes character
Fixed an issue causing the encounter panel to display characters in the wrong order if there is a global character
GMs are now able to change the layout of add-ons for savegames (active sessions), as well as add new add-ons for already ongoing sessions
Fixed player character being teleported incorrectly when GM takes item that player was sitting or lying on
Users no longer lose Action Points when the GM manages their items during combat
Fixed exported characters not having the correct skills memorized
Fixed item use state being broken after GM has moved it to his inventory and back into the world
Fixed peace mode after saving and loading
Fixed cancel button in Level Templates search field
Fixed swapping around items not being synced correctly to clients
Fixed being able to load a pin with a deleted scene
Fixed Character Sheet background after managing a Character
Fixed incorrect tier of items being generated for creatures
Fixed GM not being able to do a GM roll during combat when possessing a character
Players can now load add-ons when loading a savegame

Modding
Fixed an issue with downloading add-ons from the host when entering a multiplayer game
Fixed a possible global entity duplication issue when downloading an add-on into an existing campaign
New items in mods now get added to an existing savegame if the savegame already contained the mod and the mod is of a newer version than the version in the savegame
Mods now get loaded after the lobby screen in order to avoid players having to download mods just to enter the lobby (for Campaign and Game Master)

My Galaxy client keeos trying to download the patch but fails every time. I cannot even play the game without this update. Could somebody help me.

Try a complete reinstall?

Been there, done that.