Excellent points, for me it's about both the sneak attack and out of combat stuff. Priest of Skaen it is I spose (probably a variant of your Schemer's Needle that I saw in the builds list)
I think the idea of a former slave realizing that Skaen isn't about revolution/freedom and more about bloody vengeance that destroys slave and master is an interesting concept. iirc PoE priests are more about personal faith than direct divine power.
Thanks!