I've finished the campaign, and I'm going to try and keep this post short - the campaign does not get better in the back half. Strangely, none of the last 6 chapters has more than two missions, so the parts of Westeros' history that might be most interesting to fans of the series get the least support. Also, the game has a weird habit of having you play the historical loser in its various missions, so you have the odd and frustrating experience of winning the mission and then being informed that the character you were playing later met an ignominious death..
Luckily, none of the later missions are as frustrating as some of the early escort missions, although they do have some problems of their own. The last mission, in particular, is not very good. You control Stannis Baratheon's troops against the wildlings at the Wall, and it is, relative to the forces you typically control, epically huge. Unfortunately, the AI is terrible, and you can manage to fight one enemy unit at a time, rendering the battle trivial.
With the campaign out of the way, I will now attempt House vs House mode, which is undoubtedly the real meat of the game.