I got a 2012 E70 35i Sport, same issue at 15k miles. I hit a pot hole 5k miles ago, so I thought that was the cause. Now reading this thread, I realize the X5 alignment is setup to pull to the left causing the left front to wear first, then right front, then rears.
I hate my noisy and heavy Dunlop RFT. I just ordered a set of Continental ExtremeContact DWS (non-RFT) for all 4 corners. I hear amazing reviews on these shoes. They should be quiet and drive better. For the price of 2 front Dunlop RFT, you can get a set of Contis.