In pve, voidwalker is the least powerful. Your Nova bomb won't kill armoured monsters. And if you use the one we that traps them it becomes even more useless. I was running stormcaller last night and witnesses someone using Nova bomb on armoured targets. All it does is push them away and they walk around the bomb. Sunsingers can pump out a ton of damage. Use heart of praxic fire and use the setting that gives you longer supers. You can throw about 10+ fusion grenades which can two kill most majors without shields. Just don't use resurrection. Use the armor one which gives you more super than resurrect.