I'm not aware of any formal document, but I do know most of it from memory:
- The vast majority of balance changes were actually bug fixes with small balance implications; eg, the mercy hitbox was too small and projectiles would occasionally miss it, or the UEF T3 bomber's energy cost increased to match the other faction's as the original value was a typo.
- Naval wreckage was a feature decided on by Ze_PilOt and integrated from a mod made by someone called "ToxicFrog".
- Bomber reload time increase was decided on by Ze_PilOt to combat what was technically a bug in the bomber scripts.
- The biggest batch of changes is probably 3615, which were the result of much discussion and testing with the members-only balance forum, in an attempt to revitalize underused units (firebeetle, scathis, etc).
http://www.faforever.com/mediawiki/index.php/3615 - T3 naval was one of the changes which had almost universal support, as it was considered too cheap before.
- Shield and intel changes were both designed and tested by Ze_PilOt.
- sACU rebalance in 3619 was largely due to pip's extensive testing and modding:
http://www.faforever.com/mediawiki/index.php/3619