In addition to the ability to tame and ride dragons, Patch 4.5 includes a way to keep gear from blowing up when a regrade failure hits, improved regrade rates, Shadow Invasions, crafting requests, and a battle balance.
The latter is “a major overhaul of ArcheAge’s skill trees and effects. Many skills have swapped trees or been removed from the game completely, so visit the skill section to check your builds and adjust accordingly.”
One feature has been removed for this patch: Faction chat is no more. See Nation chat for all of your well-reasoned and mature discussion needs.