I didn't feel like I grinded a lot. You just need to figure out their weaknesses and pick the denpas that are strong against them. You can actually beat them easily even if you're under level.
Here's a tip.
Aside from the obvious fire strong against ice, it's also strong against another element.
Each element is strong against 2 other elements. Which means, each element also have 2 weaknesses.
Exception to dark and light, of course.







