I agree. I've seen many comments about how shallow her performance was.
The impression I got of Cate Blanchett's performance was of a woman comfortable with her power, yet distracted and never at ease with the visions that she alone can see. Knowing that something terrible is coming and not knowing if she can resist it. It is this sense of foreboding that keeps her from being able to fully concentrate on the here and now.
In this way I felt Cate pretty well nailed it.