These are the changes of ARK: Survival Evolved’s Patch 185.4, grouped into categories for clarity. If not otherwise indicated, they’re quoted from the relevant Steam Thread.

Game Changes

• Mods will now download dynamically upon connection even if you connect to a server directly thru the Steam Client
• All Chat is now logged to RCON
• Max height of structures above the ground is now 25,000 units. Previously was 15,000 units.

Bugfixes

• Fix for AMD GPU shadow flickering (partial… can still flicker but far less frequently. full fix is coming this weekend)
• Eliminated issue where large amounts of structures could cause client disconnection or bandwidth starvation (mega lag)
• Mods will now load properly on clients launched with commandlines (such as -nomansky)
• Fixed some more Admin UI crashes 😉

Performance

• Approximate 10% Dedicated Server Performance gain
• Approximate 80% faster savegame load speed
• Reduced client hitching around large structures
• Improved client physx performance onto large structures

(Original Announcement on Steam)

Here are the patchnotes of the previous patch (185.3)