Normal too easy, Hard too hard.

[Prodigal]

You can alter the battle difficulty but pressing Esc in the campaign map, select the Game Settings option, there's a slide for battle diff. settings, & you can alter the battle duration too.

[Monk]

You can alter the battle difficulty but pressing Esc in the campaign map, select the Game Settings option, there's a slide for battle diff. settings, & you can alter the battle duration too.

Yup. Very easy to miss, not sure why they put it there.