It's a real shame that one of the most interesting and difficult characters mechanically is mostly useless in comp. A combination of her low health that's bursted down very quickly, an unfavorable netcode, lack of vertical mobility, and a heavy disposition toward 6v6 teamfights make it a tough time to use her outside of pubs.
My biggest issue with playing her is the netcode. There's always a huge discrepancy in the death recap between what actually happened (and killed me) and what I thought happened. It makes it impossible to play the hero to her full potential because you need to play so much safer than you should have to.
I talked to mabel who plays a lot of tracer and is a game programmer himself, and he said that there would almost certainly be hit registration tradeoffs for making the game more amenable to reactive play. He also said that the way a lot of the abilities work that the benefit would be less than people think if they still wanted to keep in a moderate amount of lag compensation due to the way the abilities work. Still, I'd personally take that tradeoff for the ability to actually be able to dodge roadhog's hook or mccree's roll/flash bang death radius.
I feel that she can straight out die to so many things without having too much of a chance to avoid it (due to what enigma said), it just means that her ability to be useful is just so much lower in a comp match. I don't think raising her health is the solution though, would make her way too strong in pubs I think.
she really needs more health... in theory having 150hp probably makes sense based on her design but since so many weapons have enormous inescapable hitboxes you can get instagibbed so easily. her ranged damaged is also outclassed by genji who has more health?? not sure how that is supposed to be balanced
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