Hack is not invisible. She is IMMEDIATELY visible when starting the hack.
I’m not saying I’m happy about where Sombra is at, I think her rework was awful and on exacerbated the issues people had with her.
If you can’t react to her when she has to hack you, then aim and shoot virus, you might have other issues tho like positioning, etc.
Shooting virus immediately out of stealth isn’t really an option against most heroes anymore, which was her most problematic issue in this rework.