If there's one issue I'll complain about, it's that the game isn't the most balanced thing in the world.
Narratively speaking, it makes sense that the MC is weak at first, so the nun is doing most of the heavy damage in the earlier levels.
The problem is that she never stops doing said heavy damage.
All you need to do to consistently get out of the first area is amass 3 skill points to unlock her Holy Smite skill - a cheap nuke that will kill every enemy and boss relative to your level in 1-2 hits.
I don't know if there's a trick to it, but I've never once been able to get the MC to match that power level. This wouldn't be so bad if it wasn't for the fact there are battles sprinkled throughout the game that essentially disable the nun.