Looks like a change to his damage formula, on a few of his skills.
Ultimate:
Old: 0.45 * Magic Attack + 75 * Skill level
New: 0.45 * Magic Attack + 100 * Skill level + 100
Blue Skill:
Old: 0.3 * Magic Attack + 40 * Skill level
New: 0.3 * Magic Attack + 75 * Skill level + 150
Having the 2nd highest magic penetration in the game should allow him to put out significantly more damage than before!
Thanks to LoadRunner for data-mining this information!
Edit History:
Changed "MA" to "Magic Attack" for the sake of clarity.