Okay, so I'm in chapter 11, and I ran into a very good spot for grinding. I run up this hallway, and a door opens during a cutscene, revealing a. I saw the item node near it, and my eyes lit up.Spoiler!
10 tries later, and I gave up. I'm not sure if my party isn't strong enough, or if I'm doing something wrong. I've tried having a constant Sentinel to take the hits, but sometimes it manages to even kill Fang (my sentinel) in one hit! I've also tried to keep a saboteur on it, so it keeps using that "steam clean" move, but it instead uses moves MORE POWERFUL than the cannonball one!
For reference, my character levels are 4/3/3, approaching 4/4/3. I have a tier 2 weapon for Lightning (Helter-Skelter), a maxed tier 1 weapon for Fang, and a level 1 tier 1 weapon for Vanille (I know...).