Hey there, these exotics are coming from Excision specifically looks like a bug with the power value. Exotic Engrams can only drop 'World Drop' exotics; the ones that are in the general loot pool with no prerequisite, and it can drop rerolls of any gear unlocked through its official source. Once all World Drop exotics are earned, Exotic Engrams will start dropping duplicates. They cannot give you an item that has to be earned from another source - for example on your Hunter you need Relativism, which comes from the Dual Destinies activity, and Gifted Conviction, which has to be focused from Rahool under his new Novel Decryption option (once you reset his ranks once). Likewise all the weapons that you need, come from other sources like raids, the memorial kiosk at the Tower, exotic quests, etc.