This is a video game you need vertical item progression ... First off that bow is not that good apart from having an good effect look. Second do you really need a fireball on every class??? i would say no, not at all. infact i would slap that to a class that can cast it already if anything and even then fireball should be a spell always not an item. SO not a fan not really. LIke i said the healing staff is ok because it adds a new thing and the casting is interesting(will walls block those orbs?) But again i would limit the class that can use it.
You get the same robe it's just for poison btw...

Casters can use other weapons as well so focusing on staffs only is bad but ok larian does the same thing wish they didn't.

What are this useless items you talk about? Can we get examples maybe they will fix them.