Sombra discussion eh? I know I'm not Anne, but here's what I think about Sombra's viability.
She is very situational at best.
Clearly, the majority of her kit point towards her being supposed to be a flanker. She can pick off people, she has the means and mobility to get into the enemy backlines, and she also has a way to both bolster her survivability and deny enemy flankers the same by hacking health kits.
However, the problem I feel she has is that her damage output is just low enough that she can't reliably pick off people. Her mobility options are nowhere near as reliable as those of the other flankers. If you set up her beacon in a safe spot before engaging, you have to be really fast - 15 seconds to get behind enemy lines, get a pick off. Otherwise, your beacon will be down. If you don't use it before engaging, it's very easy to follow the trail it's been thrown to, and unlike Tracer, Sombra cannot do additional blinks. The stealth is an awful mode of escape, it only is useful as a tool to get behind enemy lines, the startup just is too much otherwise.
Meanwhile, Genji, Tracer and even Reaper have a fairly easy time getting out of hairy situations, and they also deal much more and, more importantly, more reliable damage. If they engage, they will most certainly get at least one pick before retreating. With Sombra however, it's a gamble. But not only is it risky, she also has to commit so much time to setting up her engagement and still might not be able to get out that it's extremely difficult for her to get a reliable pick. This is especially true if she tries to pick off the healer, aka Ana, who can use healnade and sleep dart. So unless you also spend the 2 seconds to hack Ana, she'll easily hold her own and maybe even kill you instead.
Beacon has a 6 second cooldown after being used or the timer running out. That's a potential 21 seconds of downtime before you can re-engage. To compare, Tracer takes 3 seconds for one charge of her blink (so she has 2 blinks in the same time it takes for Sombra's beacon to come off of CD), Genji's dash has an 8 second cooldown, which gets reset if he scores a pick and he also can double jump and wall climb infinitely.
And sadly, her utility simply doesn't make up for her being a much less reliable flanker than the other flankers in the game. Her EMP is great, but only if you have teammates who really know how to make use of it. Her Hack on enemies is okay, but situational. Her Hack on health kits is okay, but situational (health kits generally are not where fights tend to take place), and also take ult charge away from the healers.