Ok, I'll admit I'm not a lore nerd, I only follow main story + whatever comes into my attention. In WoD Khadgar is the main protagonist, working with both alliance and the horde, helping to save everything and everyone from the evil iron horde and Gul'dan. He is very powerful, ominpresent and seems to care about Azeroth a lot.
So where was he during WotLK, Cata and MoP? Surely Lich King, Deathwing and Garrosh were a great threats to Azeroth, so why he was nowhere to be seen, helping us in whatever way? What was he doing? Surely there must be an answer to this in some novel or side story, because it's looks rather weird, that he didn't care to help us fight against those threats, chilling in his mage tower, and suddenly in WoD, he cares so much?