The folks at Ferrago have written up a review of Dungeon Siege II: Broken World, giving the expansion pack an overall score of 59%.
Laid bare, Broken World isn't much to phone home about. If anything it casts a dreary shadow over Dungeon Siege II, a game that while far from perfection was solidly put together and worth recommending. This expansion on the other hand doesn't really offer enough either in terms of single-player, or the unchanged multiplayer features. For those interested you're best off with the main game, for everyone else, don't worry, it's okay to feel apathetic about Aranna's fate.