User blog comment:Starchythepotato/Future Units - Old Units' New Forms/@comment-26333435-20150620203950/@comment-26333435-20150620212253

A lot of people (including myself) use 5* Hero for cost-limited quests/missions. He's great for only 0 cost. He can also save you if you're having trouble with party cost limit.

Well, it's pretty obvious that future characters will be stronger than old ones. However, not all of them are obsolete.