Guide: VAS (Void/Arc/Solar) what are they good? Positively damaging (on shields)
Purple, Blue, Red oh my. It makes my Fusion Rifle kills banish to the realm of nothing in pretty colors! But like some games, does this elemental damage have some additional effect, like a slow or poison?
No they do not. Which is not entirely clear like most things in Destiny.
So what is it good for? Enemy Shields!
You may have encountered one of these already. Dumping a 72 mag auto rifle into a Wizard, who is glowing Red like something is partially blocking your bullets. You may have even noticed the Wizard has a white bar on top of his red health bar, much like Guardians have and noticeable in PvP. That is right, some enemies have the same Darkness/Traveler voodoo magic that Guardians have, the fast regenerating... Shield. Like Guardians, enemy shields regenerate quickly after 5 seconds or so after avoiding Guardian fire. The one big difference is enemy Shields are weak to 1 of the 3 elemental damage types while resisting Kinetic (most Primary Weapons) and the other 2 elements. On some Strike/Mission modifiers, the shields will 90% (estimate) resist Primary fire.
You can tell when your current weapon is not strong against a shield when Resist or Immune popup messages appear instead of your damage numbers. Sure your Primary Weapon will eventually eat through the shield, but if you let it regenerate, you have to take it out again. In the harder modes it is near essential for the Fireteam to coordinate element types and when someone is dropping the shields on a Ultra/Major (High HP, yellow health bar) enemies.
Red = Weak to Solar
Blue = Weak to Arc
Purple = Weak to Void
Normal - Wizards, Centurions, not sure what else has shields, but not many do and they are rather weak.
Heroic - Shields resist Kinetic (non-elemental Primary) and the 2 other elementals
Epic - Shields resist Kinetic + 2 other elements more or are near immune (only seen Immune in the Epic Thorn Strike)
[u][b]Enemy Shield List[/b][/u]
Fallen Shanks - Fire (only on epic I think)
Cabal Psions (only on Epic I think)
Vex Harpy (only on Epic I think)
Captain - Arc
Shank - Fire (epic
Knight - Arc
Wizard - Solar
Minotaur - Void
Harpy - Arc (epic)
Centurion - Solar
Psion - Void (epic)
Aim to have a well rounded arsenal that includes all 3 elements for your Special and Heavy Weapons. If you do Vault of Glass, there is Primary Weapons that have Elemental damage. Solar Scout Rifle, Void Auto Rifle, Arc (Hand Cannon or Pulse, have not seen them yet).
There is the special case during Void/Arc/Solar Burn modifiers where those elements do bonus damage. The bonus damage sometimes allows that element to eat a shield that it is not strong against. Test it out and see how well it works for yourself.
(I can not remember if Colossus or HobGoblins ever get shields. Or if I missed anything else.)
Looks pretty complete. I don't think I've ever seen a shielded colossus or hobgoblin. I'll add a couple notes:
1. You generally want to run with one of each element for your sniper/fusion/rocket/machine gun.
2. Elemental shotguns aren't terribly helpful in higher level PvE content, as once you're close enough for it to be effective, you're toast anyway. This is especially true if the Lightswitch skull (enemies do bonus melee damage) is active.