Hi:

The key thing to remember is that agile projects, for project scoping, estimating, and in order to determine and prioritize the iterantions, require an up front big picture that is properly partitioned and shows the essential high level functions and - especially - their interrelationships.    I use minimalist data flow diagrams for this.

There are other small picture analysis tasks, but frankly, the real important BA task is creating the big picture.

Tony Markos