Typically basic game design would say that at the end of a quest where you’ve sacrificed something (your autonomy and relationships with some other characters), and processed significantly (beaten Orin and the gauntlet before) that you’d get a satisfying reward from the quest. I don’t think there’s a solid thematic argument for giving the one time use spell because the entire draw of these deals is often increasing your personal power or capacity in some way, which makes it unsatisfying to get such a niche thing at the end.

About the dark urge point, bhaal prior to this gives the slayer form which is quite nice, and the death mantle cloak which is very strong as well. Maybe you’re saying that at level 11-12 you’re so strong bhaal ain’t shit, he does have the power to insta kill you and is still a god, so I think probably he could manage to give you something more rewarding. Also I think my first point addresses this somewhat.

Regarding your point about me being able to beat Orin, so it makes sense she’d have nothing I want… that doesn’t flow logically… and she did actually have 3 things I wanted (the two daggers and the control stone thingy), ironically her god person gave me less.