I have visited Xûr this weekend and when buying the special engram called "isochronal engram" (fated engram) that costs 97 legendary shards, it gave me something that I already have in my collection (in this case "Synthoceps" gauntlets, bought with my Titan character). I am currently missing 2 exotic armor pieces for Hunter ("Khepri's Sting" and "Assassin's Cowl") and one for Warlock ("Stormdancer's Brace"), but I have all exotics for Titans.
Is the fact that I didn't have one of the missing exotics normal ? Are they locked by any quests, triumph, achievements,... ? Or am I supposed to buy the Isochronal Engram / Fated Engram with my other characters (Hunter and Warlock) for it to give me the exotics missing from my collection ?
Thanks in advance for any answers.