I'm not very enthusiastic about a rune that is 'don't roll for misfire'.
I mean, yeah, if you're sniping Malekith, it's probably good to have, but if i spent several favours in making a awesome dwarf rifle i would be a bit pissed if the critical assassination roll had 3 rolls (misfire, aim, and reaction of target), instead of say, cleaning the chamber the day before.
Also fuck getting more skills for shooting good, hell on the action economy and traits that could build on the traits we already have (unless master assassin counts or whatever it's called).