Your entire argument is that she is good with supports… this was the whole problem with Ashe. She was trash, but good with Mercy damage buff. She still got buffs though, because she was weak on her own. I’m not saying she needs specifically a damage buff, but she definitely needs more kill power, perhaps with a bit less falloff so she can keep a bit more distance.
TBH this is her biggest problem. Her character is overall bad at dealing damage, but her ult is built so easily. I get it in the first team fight, just by spamming tanks with damage from behind. My biggest issue is that. She isn’t good unless she is attacking tanks to build ult charge. I don’t have fun poking a roadhog, and tping away before I get hooked, but it builds her ult so fast it is the only real thing to do.
Part of this problem is that she has no in-fight mobility, such as heroes like Tracer, Genji, Hanzo, Widow, etc. They all can escape or use mobility to help fight. Sombra, on the other hand, even though she basically has a get out of jail free card, she has no mobility to help her during an actual fight. Invis is easy to get knocked out of if you use it in the middle of a fight, and translocate is a relatively slow travel method, and is predictable because you know where they are going. So, for example, even if I’m at 145 HP as Sombra, I might dip out of a fight if I’m concerned about a headshot. I’ve seen really good McCree’s get a lucky headshot that just obliterates me before I can react.
Let me be clear, she has nice damage up close, but she has no abilities in her toolkit if she doesn’t ruin another hero’s kit. Sombra isn’t really great against killing DPS (better things to do, ya know), so I wouldn’t waste my hack on him when tanks like Rein, Sig, and Hog are better uses. So, if I only have my primary fire, and I get caught needing to reload, I’m forced to leave because she has a long-ish reload (I think like 1.45 seconds?)