His likeability has come at the expense of other characters. They made Garrosh the biggest douchebag in the world to clearly contrast as far worse than Varian at his worst. A lot of Varian's development is locked away in books as well but a lot more of it has to do with building him up as an avatar of Lo'gosh which kinda sucks as its a free pass to automatically convince other Alliance races, like the Night Elves and the Gilneans that he's a chosen one. Rather than having to prove himself to them, they have to prove themselves to him. It's a wretched bit of development.