I think Wattson is perfectly balanced at this point. Her Ult has fantastic utility for anti 3rd partying which was desperately needed because of how ridiculous throwable spam was. Some teams now will at least be smart enough to think and look at the end of a battle to see if there is a Wattson with her Ult up before wasting your throwables.
Fences reward smart circle rotating play by being able to hold down buildings. Being able to rotate properly is an underlooked aspect of BRs by a lot of people I think. So if you aren't the best shooter you can still manage to compete and she really helps to magnify that if it is your strong suit.
Her personality/voice acting is great too. Both Octane and Wattson have been home runs for the DLC characters in terms of balance and can't wait for the next one.