Lets try using Lighting Surge on the original subclass it was designed for. We know Prismatic Lightning surge is really good, but how about Stormcaller Lightning Surge?

1. Add Clear Lightning surge - Kills most GM red bars and applies jolt to anything that survives. Really good ability to build stacks for Ionic Sentry. Ionic Sentry - Passive damage that grants bolt charge which feeds Lightning Surge Psychopomp - Amazing add clear weapon. Rolling storm feeds Lightning Surge and final blows feed Ionic Sentry.

2. Priority Targets Chaos reach and Heavy weapons are the main tools for dealing with priority targets like Champions. Ionic Sentry followed by Chaos Reach is pretty strong. Queensbreaker and Legend of Acrius are great heavy weapon options.

3. Survivability Karnstein with Lightning Surge gives Stormcaller the survivability it needs. Karstein Finishers grant Restoration x2 and Proximity Ward grants overshield during the finisher animation. So finishers are a great way to heal with this build. Restoration + Amplified provide enough survivability to play aggressive in GM level content.