Well the Steelers Defense lost a lot of leads last year, their running game was about average, and their offensive line is near as bad as the Bills. Ben threw for 4300 yards last year, while being sacked 50 times.
So Buffalo doesn't quite have the receiving core, he might ONLY throw for 3900 yards. Obviously there is so much wrong with Buffalo, but Ben would be a solid instant fix at the most important spot on the field.