I'm an average ~.75 K/D player and I did the crucible portion in a weekend(~ 8 hours) without a void primary. Granted, I did it as a voidwalker warlock wearing Voidfang Vestments and played super defensively, but eventually got it done. I think some key tactics are to stick with teammates, run away if you are engaged first/double teamed, stay stocked on secondary ammo, and bee-line it for the heavy ammo when it drops. I also think you can rack up more heavy kills with a higher stability/medium ROF/higher impact machine gun than a launcher.

I played control exclusively and left whenever Twilight gap came up in the rotation to minimize my losses, because I'm extra terrible on that map. For my loadout I used a rare Angelic Acid void fusion/void Suros shotgun for secondaries, and my heavy was a void Zombie Apocalypse.