Yeah, SH doesn't need the Gloom at all, she'll be super-invisible.

If that, I'd go Cleric 9 / Thief 3.

That way, you get:

2 times an ASI/Feat
5th level Spells
Bonus Bonus Action, great for a cleric [or for the hand crossbow]

Or

Cleric 8 / Thief 4
+ 3 times ASI/Feat
- No 5th level spells

Fear my wrath, for it is great indeed.