Via the latest patch, Bungie has toned down the challenge in some of the key missions in Destiny, as well as addressing issues that were affecting some players who slogged their way through the Vault of Glass raid. Here's the patch notes via Bungie.net:
Missions
• Shrine of Oryx: Reduced difficulty by removing majors from Heroic tiers
• Sword of Crota: Reduced difficulty by removing majors from Heroic tiers
• Exclusion Zone: Reduced difficulty by removing majors from Heroic tiers

Raids
•Dropping the relic at the end of the raid will no longer result in a team wipe. This will prevent players being stuck at a black screen after the raid.
• You will remain dead if you were dead when the mission ended. That will be addressed by a future patch.