@Rahz_VII I'm on xbox. No doubt the blue line makes it easier for them to follow you. But when octane is in his boost run, there is a green line.. Octane can also still be shot while he is in boost mode. Then there is Mirage and his Ult.. You can still track him various ways.
Correct me if I'm wrong, but I think your frustration is coming from how you use the void. I think you're using it as a "I'm almost dead run/escape" ability. There is nothing wrong with that, I do too. How ever you have to keep in mind with or without the ability you were about to die anyways. During those instances the ability just gives you a slightly better chance at survival and getting away. Is it full proof? Nope, but it does work some of the time.
So how OP would wraith be if she did not leave a blue line behind? You would basically be able to disappear on enemies anytime you were close to death. Pop a few shield cells/batteries or flank them and kill them.
It's sort of like her portal and abilities in general. Sometimes it's really, really effective and OP to the other teams. I've used the portal to teleport into a really hot zone, pick up team mates banners and get out. I've also used it in Cities. My team will be getting pinched by two squads and it's certain death. I use her abilities to put a portal to a different building. The two teams who were pinching us end up fighting it out. We then teleport back and third party them.