So I made a report on this at the start of the expansion, would still like to highlight how poorly this ability is executed:
Killing Spree only scans for targets on the initial button press, once the button is pressed, only the targets found on this scan can be targets for killing spree.
The rogue teleports behind target #1 and both weapons hit.
Of the initial targets, target #2 is selected, however if target #2 is no longer in range, the rogue does not teleport and no weapons hit.
All 4 attacks after the first attack can choose a target that is not in range, this means only the first hit is guaranteed, and for any targets that fail, the rogue is effectively stunned for the remaining duration as they do not have control while killing spree is active.
I would like to emphasize the wording of the killing spree tooltip:
Step through the shadows from enemy to enemy within 10 yards, attacking an enemy every .5 secs with both weapons until 5 assaults are made
It seems ridiculous that I can walk into a group of mobs that’s less than 10 yards in diameter, and if it picks a mob on the edge of that circle, I can end up only hitting one target if the other 4 attacks pick a mob on the opposite side of the circle. What is even worse is that mobs with large hitboxes. If a mob has a hitbox 20 yards in diameter, killingspree will teleport to the center of that hitbox from 20 yards away (10 yard radius+killingspree radius) and then be unable to reach any targets that were where the rogue was standing.
In short, killing spree only works well on single mobs, once you have a second target the ability starts to fail attacks and 5 assaults are not made, despite that being the whole point of the ability.
It would be easy for the ability to scan for the next target after landing an attack, yet it is coded to waste attacks for no reason other than being lazily programmed.