I have mixed feelings. The good thing is that lost sectors are easy even solo. So you can speed run ones you're comfortable with making the lower drop chance not feel as bad. And it's also targeted loot farming. Meaning for those who want to narrow down the drops for Stat roll purposes. That being said I think after it's dropped for you once and/or after a set period of time said exotics should also be put into world drops/exotic engrams.