My Xcode 9.2 is hanging when ever tried to open Storyboard. I have tried reinstalling the Xcode 3-4 times but not working for me, hanging is only happens for storyboard. Other part is working fine.
From the video you posted, the time seems normal. This is due to the fact that there is a lot of info that needs to be loaded.
What you can do is split your story board into smaller ones.
Just to double check if your xcode/machine works fine, you can create a new project and open the new storyboard. I imagine it will still take a few seconds but you will have a reference behaviour.