Widow's problems show the most at high-level play, where basically 2 players (the widow on each team) are dictating the outcome of the match that's supposed to be 6v6. Rarely do you see snipers that good in our skill levels but even so, frequently the best answer to a decent sniper is to out-snipe them. The counter to a character being "play the same character, only better" means that character is not in a healthy spot.
Also wtf at complaining about D.Va ult. I think I died to it once or twice on my first day and never since. It's stupidly easy to dodge, 3 characters can hard counter it without ults and like 3 more with ults. It's a zoning ultimate just like high noon, it's to make people leave an area, which it does pretty well. It rarely gets any kills.