In the second part you almost need to use the DV's. Once you use the three initial DV's, a fourth is created that moves part of the map and gives skills. I had Owain/ Odin activate it, but left Inigo/ Laslow and Severa/ Selena on the section that did not move, and trying to move them up through the two berserkers in the forts along the curved path was painful(eventual deaths). And the skills from the fourth DV give a huge advantage fighting the boss.
Overall I thought these maps were fairly easy, once you figured out the tricks in each one, they became easier.
EDIT: Has anyone tested if you can get multiple Fell Brands?