Level up your heroes? They don't seem to be at their max level yet according to their ascension levels. Searching formations on youtube would be a good idea, they helped me out a lot.

Take this video as an example: https://youtu.be/xxEUr6DpKEU

I would lv grezul as far as u can then put him front row with lucias rossaline following grezul belinda and

ira