Toyota chose the OEM tires because they have low rolling resistance, and give you the best fuel economy. The Michelin Energy MXV4 tires have, I believe, the lowest rolling resistance of any available replacement tire.

30K miles on a set of tires can be very good or very bad. You have to compare with other tires on the same roads. Some areas of the country just have very abrasive roads, and tires in those areas just wear out quicker.