Ubisoft has outlined the changes in For Honor's Day One patch, which is described as "a high level overview," with future patch notes being more detailed. As you can see below, however, Ubisoft are instead showing the biggest things being changed upon release:
Matchmaking
All countries around the Mediterranean Sea are now part of the European region.
Heroes
Collisions improvements and fixes
Improved animations
Audio
Audio balancing fixes and improvements
User Interface
Fixed a memory leak
Fixed occurrences of major framerate drop
Improved flow in and out of the invitation menu
Multiple localisation fixes
Additional Fixes
Stability fixes
Connectivity and matchmaking improvements
Metagame bug fixes and UI improvments
Hero Balancing (based on player feedback)
Fixed minor issue with the round counter
General bug fixes
Ubisoft made clear, however, that hero balancing was already implemented in beta testing. Has the beta testing helped significantly improve the game?