im no expert on overwatch, but i am rather seasoned in precision first person shooters.
in CounterStrike, i play at 800 dpi with a sensitivity of 0.8.
i was stuck in the silver leagues for many many games, the thing that helped me escape was to reduce my sensitivity drasticly, i went from a sense of 3 to a sense of 1 and in only two weeks my HSR quadrupled and i shot up in the ranks significantly eventually settling in the LE range after around 2 months.
if anyone is having trouble with aim in any fps, i always say the same thing, halve your sensitivity, if you are only using your wrist, then your sensitivity is too high, your whole arm, or atleast your elbow should be used.
i find that the general rule is, you should reduce your sensitivity as low as you can get it, while still being able to do a 180 degree turn without running out of mousepad any lower and you will be unable to flick to certain directions without lifting your mousepad.
the lower your sensitivity is, the more accurate your shots will be, so it is in your best interest to reduce it as much as your mouse space allows. it will feel slow and clunky, your reaction time will be terrible, but if you practice, and make sure you never lift your mouse then after playing for a day or two you should feel comfortable, and after a week or so, your reaction time should become more or less equal to whatever it was.
perhaps the pace and field of play that overwatch provides would require a higher sensitivity, thats a question for the proffesionals to answer, but the same basic principles apply: a lower sensitivity will always be more precise, so you should lower it as much as you can until it makes you incapable of performing neccessary maneuvers.