Yeah, Blood Stalkers are odd. I’ve taken five to snipe characters, with their 24” range and chance for mortal wounds, but never seem to roll sixes when I need them. I’ve had a bit of success using them to defend an objective in my own zone, shooting anyone who pollutes my side of the table with their “feet”. They’re pretty solid vs cheap infiltrators.
They’re better paired with Morathi, to get an extra round of shooting in the Hero phase. They can’t cause mortal wounds in that round however.