Some heroes receive bonus stats in certain parts of the game. From the in-game loading screens.

Story Missions

Jake (warrior)
Cecil (rogue)
Chaos (archer)
Gordon (acolyte)

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Raid Missions

Faye (warrior)
Izumi (rogue)
Nadia (archer)
Kahuna (acolyte)

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Arena

Loki & Fenrir (warrior)
Makoto (rogue)
Zack (archer)
Arisa (acolyte)