Anduin's biggest changes actually happened outside of the game world, most notably in the World of Warcraft comic series and in Christie Golden's companion novel to Cataclysm, The Shattering. In The Shattering, Anduin comes into his own through a series of adventures with Jaina Proudmoore, and by participating in the burgeoning dwarven civil war between the clans at Ironforge. The prince finds his path with the Light, determined to become a priest instead of becoming a warrior like his father. His character has grown considerably since his inception, with Blizzard making a concerted effort to move his story forward against the backdrop of the cataclysm.
I was a fan of Anduin in The Shattering because he was written to be a spiritual opposite of his father. While Anduin retained his father's caution when dealing with the Horde, he seemed more open-minded, forgiving, and willing to compromise on things above and beyond him. There is definitely groundwork being laid for a strong, compassionate leader, something the humans have not truly had since Varian's kidnapping and King Terenas Menethil of Lordaeron.