I've been testing replacing Shotgun with Elemental. So far I've found my highest DPS from Fire Bolt (no passive) and Crystallized Flame (w/passive). Energy for the offhand is never an issue, simply keep heat high and time your attacks to ensure Voltaic Shunt procs every 10 seconds. Using Effects UI makes it much more effective since you have actual visibility to the buff timing. I found that Desecrate was just using precious Energy that was better spent casting Maleficium instead. With Fire Bolt, you have plenty of Elemental Energy so Crystallized Flame works well as it is cheap and high damage. In high mobility fights, it's likely not as useful, though. Mjolnir is still good damage as well and aligns with Voltaic Shunt, but it's Energy hungry and doesn't recover from potential rotation mistakes as well as Fire Bolt. It's probably the most basic and simple to use l, though. It's also the better choice for high mobility fights where Crystallized Flame may end up wasted. My Shotgun build still does higher DPS than Elemental, but not by much....and it does feel like it needs more management along with no AoE capability.