I like Holy Knight for Marianne, since all of her grab bag of proficiencies seem to fit the class best. Also, I'd say Dark Knight fits Lorenz better than Hubert. Not like he has much Speed. I've never thought of Valkyrie Marianne, but I guess it might work.
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Also, I actually have positive memories of my first GD playthrough where I made Hilda a GK. She activated Pavise pretty often and was a good mobile Glacier.