My opponent had Bruvac in play and I cast The Tale of Tamiyo. It milled about 60 cards but I only drew one card. It just kept milling and milling, and I didn't stay in the game long enough to see if it would mill my entire library. I just quit out of frustration. I'm assuming this is a bug. There were no other permanents on the battlefield that would have affected the Saga's effect.