Auto-translated
Yes, the fire rain in this mission is very annoying. I don't remember if I mentioned advising to go to the demons first, and then to Ludmila, so that the passage to the orcs wouldn't open for too long.
It seems to have an effect. But no one will touch the castle with the main orc. Only minor heroes will fight.
It's up to you. Look at the bonuses of both staves in the main menu and decide what you need more.