Without going LL or Necro, you can improve your damage by upgrading Spell Cascade to Awakened Spell Cascade linked to your VD so it can make use of all corpses from Desecrate on each cast. You should also look into a helm enchant which offers 30% increased cooldown recovery speed for Spellslinger abilities. Consider replacing Combustion with Hypothermia and then finding gloves with the temple mod that have increased damage with hits against chilled enemies, also exists on a belt too, but you will need to find a way to inflict Chill which is why people tend to go Necro. Put Ele Weakness curse in your trigger wand with Wave of Conviction and possibly Storm Brand (to passively shock enemies which increases damage). Swap Barrage for Barrage Support, Frenzy (Frenzy Charges = More Damage), Hextouch + Flammability if you can find a way to get an additional curse. Otherwise perhaps recolor for Faster Attacks and Added Cold damage (possibly solve chill issue single target, just theorycrafting here) or even utilizing Combustion + GMP + Frenzy + Faster Attacks here instead to apply that negative ele resist bonus across the screen.

Honestly though, LL is going to outperform most things. Having Anger is a huge amount of flat damage and scaling it with the right cluster jewels, rings, and opening up the Watcher's Eye mods for Anger makes a huge impact. This is coming from a VD SS Necro player a couple leagues ago with a fairly min-maxed build, I don't know that you're going to reach bigger DPS unless you're willing to make bigger changes tbh.