Scatter Shot's range is only 10 meters. Compared with Piercing Javelin (28 meters), it truly stinks and the knock-back effect is less. You have to run up to an enemy and basically be within melee range (not a great spot for a bow to be in), whereas Piercing Javelin can knock people off keep walls from the ground; sometimes from one out cropping to the next or worse, knocks you through the grating people pour oil over. Scatter Shot? Does none of that unless you somehow managed to sneak up to there and wait for an ideal shot w/o getting detected and cross your fingers the knock-back even occurs. It also seems to have less of a knock-back effect on players than it does vs. PvE enemies, which actually get knocked back further, and acts more like a brief disabling effect like the morph of Poison Injection provide if you hit someone casting. And the knock-back effect isn't even guaranteed, but Piercing Javelin apparently is unless you are lucky enough to see it getting cast in a mob or 30 headless chickens running over each other and hold block until you can break line of sight.
I understand Scatter Shot might have been intended as a "last resort" attack to disable an attacker briefly (Magnum knocks you back 6 meters IIRC from attacker vs. stealing health) to allow for an escape, but it doesn't work reliably enough in that scenario (vs. Piercing Javelin that always seems to connect and knock you on your back, rather dramatically) at that distance and with reduced chance of even knocking them back.
Please consider buffing Scatter Shot's morphs- maybe have Magnum 15 meters + 6 meter knock-back with slightly more damage than it presently offers to be more effective in PvP combat, and give Draining Shot 28 meter range + a guaranteed knock-back.
I realize Eagle-Eye adds 3 meters to all bow abilities (makes snipe very nice when other archers can't snipe you), but even then 13 meters for SS is still too short, and the chance of getting the knock-back are not any better. Considering some of the rather detailed reductions/buffs coming up in the next major patch, it makes no sense to ignore this skill that has the potential to be more useful than it presently sits in it's current iteration.