Sounds like you need to refine your tactics a bit if you're having that much trouble. I've done every Cei'th mission except for three and while I didn't 5-star every battle, I can't say it was really frustrating aside from a select few. My characters are not maxxed out and I don't have ultimate weapons or fully upgraded accessories. It can take a few tries but when the right strategy clicks, you find yourself wondering why you thought it was hard five minutes ago lol. Or at least that's how it is with me.

What missions are you stuck on?

~DragonHeart~