Ahh brioche. 5 eggs and 250g of butter in each loaf!! I remember making it for the first time, I was sure I had misread the recipe and then I was convinced the recipe was wrong, I couldn't believe there would be so much fat (not to mention the sugar) in it.
Not sure why yours didn't rise much, mine always does a lot. Do you chill overnight before forming into balls or a plait and then leave for a second rise? I find brioche dough is very good for making interesting shaped loaves using this method, I presume the butter responds well to the bit of chilling.