The biggest change in 5.4 is for the Frost Mage. Your Mastery has changed. You no longer do increased Mastery damage Vs frozen targets. Now, a portion of the damage done by Frost bolt and Frostfire bolt is stored and your next Ice Lance will unleash those icicles. Your pet damage is also increased and various spells were buffed, such as Living Bomb, Ice Lance, and your pet’s Waterbolt damage.
Frost did get a nerf, Frostbolt‘s damage has actually been decreased a bit.
Mage Patch 5.4 Contents