I find it incredibly useful on Zane. Fire your shots above enemies heads and the electricity arcs to them and count as head shots. With Zanes “Playing Dirty” (Hitman Tree) Kill Skill it gets even more nuts as he launches 2 of the wisps. No other gun I have used benefits as hard as Kill-O does as you get twice the DPS from them bad boys. Couple this with “Brainfreeze” (Under Cover tree) while shooting the wisps above your enemies and you get a lot of easy freeze build up. Not sure how well it pairs with other VH’s but anyone that can boost electric damage or chance would probably roll hard with it. Regardless it is a very good “fire and forget” way of removing large groups of enemies shields.
It’s a fantastic Medium range weapon, too close and your enemies won’t get many ticks from the wisps arcs and the Wisp will poof after going too far so try and keep your targets at a medium-close’ish distance. The wisps will also poof if they make contact with any sort of terrain so send it down “corridors” and try to minimize terrain contact.