Marianne is quite good imo; in my playthrough GD route, I made Marianne a dancer and she really carried. Her decent speed and good mag made her a good magic/Levin sword user whilst also being able to refresh and heal units. Due to her somewhat decent movement as well she can usually catch up to units after she uses Stride, and even if she can't she still has Physic and Silence so she can still be useful from a distance. Her Hero Relic also allows her to do really good damage most units as well. She also has really good avoid if you use Sword Avoid, so she can be decent on the frontline as well, especially against mages.