As for the over-balanced assortment ratios - that's also Hasbro America's fault... and their major retailers (like Walmart) who dictate assortments.

Take a poll of regular parents or kids, or even collectors, as to which character they would buy first if they could only buy one toy (which is usually the limit of most kids & parents' budgets)... and I'd be imagining that over half would be prioritising Optimus or Bumblebee first because they are the main characters of the movie. Hasbro market research would have ascertained the same purchasing priorities with each movie, but perhaps failed to take into account that most people interested in TF3 were customers since TF2, so already had the main characters.