Generally Ashe is pretty strong.
She is a high damage, mid-long ranged dps. You don’t really see more than 200hp on any other character with these qualities.
Her damage per shot can be very punishing for any1 being hit, especially if damage boosted by a mercy, in which case she can 1shot 200hp targets with a headshot. The 12 bullets and long reload is pretty much what makes sure it’s not overpowered.
TNT can deal up to 1050 damage (175 per target hit), which in turn puts a lot of pressure on the enemy healers and give you a ton of ult charge.
Coach gun is not just used to push you back from attackers, but also push them away, which can effectively double the distance put between you. On top of that you can use it simply as a mobility tool to take better positions.
Against junkrat tire, try to get in a position where you will see the tire before it can get close to you and shoot it. It’s very squishy and should be somewhat easily killable before it can reach you then.
Against D.Va bomb, if you die to this, you most likely had poor positioning. Generally you want to always be close to cover.
BOB is like having a 7th player on your team and you control the area you need him to contest. Usually placing him somewhere he will split the enemies attention has been working the best for me.
Also, Flank Ashe is sooo sooo strong. Possibly even to a point i would call it overpowered.
Hit a TNT from behind on their most vulnerable targets and quickly follow up with scoped shots. Even a single bodyshot is enough to finish any 200hp target.
Then just keep shooting them in the back until they turn for you, in which case your team is free to push in from the other side, while you coach gun to a safer position.
Usually at this point it’s just cleanup.
This is something I do all the time when playing Ashe and it keeps working like a charm. Also against GM-T500 players.
(Most important thing is usually to find the right timing for doing this)