Sometimes you hit a bull’s-eye. With Mary J. Blige, Janet Jackson and Alicia Keys, it’s hard to imagine a trio of headliners more perfectly suited to a festival tied to Essence Magazine. Though the Essence Music Festival—which takes place July 2-4 at the Louisiana Superdome—has evolved beyond an event that caters to African-American women, that audience clearly affects the festival. It has limited its exposure to hip-hop (allowing a lover man like LL Cool J on the main stage at 8:35 ...