Is there a standard distribution of minifigs when you purchase an entire case?
Every box contains the same distribtion of minifigs. For example see this review on www.eurobricks.com of series 13 has the same distribution as my box. (links to his other CMF reviews are on the bottom of the first post)

For most series boxes contains 3 full sets and 12 remaining ones.

Series 9, 10 &amp; 11 contain only 2 complete sets, with 2, 4 or 6 bags of the same minifigs. These boxes where also available as 'half' with only 30 bags. This way these boxes contains 1 complete serie.