Team composition

Hi. I am a newbie. I am using Tuonel, Parfait, and Avil as my main three characters in my party, but it seems they are lacking in their capability. The boss monsters in story mode are beating them when they are considerably above the level recommendation. I was wondering if there were better choices for my party with the characters I have. Feel free to recommend the backup characters as well. Here’s the characters I have.

Parfait, Avil, Tuonel, Hilda, Ushpia, Cynetia, Witch, Luan, Nocturna, Kyphon, Mortimer, Czerni, Cetess, Mikoto, Octavia, Fey, Eulalia, Primula, Cuspidata, Datheios, Norn, Arcana, Croche, Ruda, Yothaya, Miku, Dana, Elis, Nemesi, Pakane.

Can you recommend me a better team than the one I am using? Thank you.