[One Vision] Advice on how to beat Cressida Rescue mission in Golyat.

I'm having a rather difficult time, even after so many hours grinding away. I've tried the battle about a dozen times, with leveling sessions after each 3-4 losses. I either manage to get to Cressida and revive, only to be stretched thin, divided, and picked off. Or, I deal with the threats okay, but run out of time.

Current setup is:

Denem: Dual 1h swords Ninja Canopus: Axe/Bow Vartan Gildas/Mirdyn: 1h Hammer/Shield WKnight Hobyrim: Sword Saint Voltare: 1h Hammer Knight Cerya: Dual 1h Swords Blademaiden Cistina: 2h Gripped 1h Sword Valkyrie Olyvia: Cleric Donnalto: Priest Arycelle: Furia Generic Archer

They're all lvl 20, and I wonder if I should keep using silver weapons/baldur armor? Any class changes, team comp changes you'd recommend? The special upgraded units are the ones giving me massive trouble, where I can't seem to take them out without running out the clock. Thanks in advance for any advice.