What a letdown, used Jessy on Insane LV in Balanced arena. She's max LV and uses Mithril Axe, only deals 6 DMG to an Archer army, use AP potion to get 50% ATK, it only becomes 8 DMG to an over 100 HP opponent, yet opponent gives much bigger DMG. Now arena is 1 vs many armies system and extremely time consuming and not very rewarding.

The balancing of the insane difficulty definitely needs some more work and will be improved based on the get feedback I get about it. For the next upload, I decreased the DEF values on that difficulty, to ensure that people can actually damage the enemies.

You get ~2 levels of experience for a squad when you finish the entire arena.
The difficulty doesn't change the rewards, which means you can rush through on the normal difficulty if you don't want a challenge but just quick rewards.