User blog comment:Linathan/Unit Spotlight: Oracle Knight Ark/@comment-26336535-20150602183538/@comment-26140304-20150603035959

Well, Ark being a 7* doesn't need to be emphasized when talking about his Leader Skill. Once Grahdens and Owen get 7* forms, which is way down the road, I doubt that their parameters boost will change much or at all. Their secondary effects, like Light and Dark mitigation and crit damage for Grah and Owen, respectively, could receive some sort of nice boost.

Regardless of whether or not a really good unit is a 6* or 7*, each of them serves different purposes in terms of squad lineup. Grahdens can serve as a better leader when facing Light or Dark enemies, Owen for crit teams, and Ark for Sparking and BB spamming.