Here are a list of valuable augments that require T6+ to obtain:
Enomuth's Bone - An adventure that begins by talking to Ikjar in The Hidden Vale by the T7 Aura NPCs. Begins the quest "Slay the Enomuth", which is an assassination mission. Everyone in the party is awarded Enomuth's Bone on completion.
Hardened Drachnid Carapace - An adventure that begins by talking to Molyr (standing next to Ikjar). Requires completion of Slay the Enomuth to obtain this quest. Each boss has a 10% chance to drop the augment.