General

The amount of guild reputation and guild experience gained from killing a raid boss has been dramatically increased, as the previous rate felt too low compared to the difficulty of progressing through raid content. This change will require a realm restart to take effect, which will be next Tuesday's weekly scheduled maintenance at the latest.
Shield of Velen guards in The Exodar are now consistent with other "royal" city guards in terms of health, level, and damage.

Classes

Mages
Arcane Blast now costs 5% of base mana before stacking modifiers, down from 7%.

Dungeons & Raids

Baradin Hold
Argaloth despawns and resets properly if the raid wipes during Fel Firestorm.
Blackwing Descent
While flying around the Vault of the Shadowflame, Nefarian no longer forces everyone to stand up if engaged.
Throne of the Tides
It should no longer be possible to summon a mount in certain areas of this dungeon.

Items

Shard of Woe (Heroic trinket) now reduces the base mana cost of spells by 205, with the exception of Holy and Nature spells -- the base mana cost of Holy and Nature spells remains reduced by 405 with this trinket.

Professions
Engineering Target Dummies are no longer able to taunt boss-level creatures.