[SPOILERS]Stuck in Gracos

Hi, new DQVII player here. Am stuck in the Gracos fight, lol. My current party is:

• Lv. 22 Hero - Fighter, five stars (Mastered Warrior)
• Lv. 20 Gabo - Shepherd, five stars (Mastered Thief)
• Lv. 22 Maribel - Priest (Mastered)

Am only doing, like, 66 damage p/turn. Graco has an HP of 1,400, meaning it'll take me, like, 24 turns to beat him...

Do any of you have any tips with the limited options I have?

And no, I do not have an alternate save file. After this battle, I'll make the habit of having a save file before entering a rune, and another one after entering...