really? You saw Robb and Tyrion grow as leaders, Theon's journey had plenty of development, Jon Snow has had to grow up very quickly, Cersei has started to show some(ish) sympathetic character, Sansa is another who has had to grow, Joffrey has become even more evil, and the 3 episode or so arc of Arya and Tywin has really developed their characters.
Add in a few droplets of the Tyrells and the story of Stannis and Davos, and I think their has been massive amounts of character development.
Possibly Bran's story hasn't shown too much character development, but has had massive story development. The only person I agree that the character development didn't happen until the last was Daenerys, but even in A Clash Of Kings, her story is dry until the house of the undying and the part after, which they haven't shown this season.
I agree though would have like a couple more episodes, but the budget is what it is, and with some massive events to come, they can't over spend now and risk cancellation