I need to start this post with a health warning. I am not a fan of the Agile methodology. I have been involved in Agile development and I have even had the dubious pleasure of being a Scrum master. I particularly dont think that Agile is a good fit for the large majority of BI projects.
The reason for this opinion might surprise you (well not really if you have read the title). I dont think Agile methodology is fast enough for effective BI development. Back up a little