User blog comment:Lord Loss/Discussion of the Week: End-Game Quests/@comment-1758220-20120809205732/@comment-2049092-20120811210945

Capcom probably just added them as extra bosses. It's just there so that you get something from ranking up after Guran Miraosu. Guran is the guild storyline final boss, and Rare Lagi and Rare Narga are just extras.