There is something incoherent between these two talents. Or, it doesn’t work as intended, or the tooltip of Pious Cut-Throat is not enough precise.
I tested in training room, this talent does not work with backstab ranged kills (as you spelled them in talent tree).
So, either there’s a need to precise here
Shroudfield give the bonus to “backstab ranged”. Tbh, I am not sure it would be balanced to allow ranged backstab to work with this talent, but at least change the tooltip to describe exactly what it does.
This one specifies that it will increase melee backstab damages
While shroudfield, that works with ranged damages, has this description