This article lists all undocumented changes for patch 3.1.2. All documented changes should be listed on the main article.
General[]
Armor Penetration has been capped to ignore 100% of the targets armor (or 1232 armor penetration rating). Before the patch it was possible to receive a damage bonus because of > 100% penetration rate.
Arenaweapons with an item level of 239 have had their rating requirements increased to 2350. (Just a tooltip change - the increased rating was already activated via hotfix)
Ulduar 10-player hard mode weapons have been updated to item level 232.
The quest markers (exclamation point and question mark) as well as tracking dots (repair service, reagent vendors, etc.) on the minimap are now larger.
Better word wrap at the objective tracker, allowing you to see again how many of the requested number you have earned / killed / found, even if there is a symbol for the quest item.