The OEM Michelin MXVs had a wear rating of less than 200 as I recall, and I ran a set of XGTVs (wear rating 170) 30K miles including a couple of hundred miles or race track hot laps. The rears tend to wear more in the center, but more at the shoulders on the fronts; 7500 mile rotations evens it out and extends the life of the tires.
It's possible that excess toe can wear the rear tires evenly. You said you had it aligned after replacing the rear bushings. What are the numbers?
If the car didn't eat rear tires before the work, then the number one suspect is something done during the bushing replacement has led to the condition.