I agree that Strix is just better than Nessa, he can deal with flankers 100 times easier, he can just burst them down with his invis, quick scope and flare, which isn't very easy to hit but not too difficult either. But Nessa isn't bad, if you're really good at her then you can really carry like Hecate in these two videos, but you need perfect aim, perfect game sense, perfect reaction time, just way more effort than you need with Strix. Nessa still has a higher damage output on long range with her two talents Eagle Eye and Steady plus she can finish people off who are low on long rage, she has a way better ult with high one shot potential especially with Eagle Eye or Steady Aim. I wish Nessa had some more self-defense on close range against flankers, but other than that I think she's still great and I love playing her.
https://www.youtube.com/watch?v=EcCvo7Z9suE&t=
https://www.youtube.com/watch?v=9uHkOrDhoWk