I believe bastion needs a nerf in overwatch because he has;
A high MAG of bullets
Reload time is too fast
Self healing is too fast
He can be Overpowered on payload matches
He doesn’t move for example when concussive blast hits him
He has a high sensitivity when in sentry. His recon has high damage considering his sentry gun does too.
His ironclad passive ability needs to be scrapped.
Hes not.
His high damage comes with a big cost. Little to no mobility.
Hes very easily countered with coordination and team work.
You are clearly very new to Overwatch.
So welcome to Overwatch.
Once you’ve adapted to dealing with a Bastion comp. it will be extremely easy to deal with him every time you see a Bastion.
Bastion is complete trash right now and you will soon realise that. Just one Sombra hack or one Sigma rock knock back is almost guaranteed Bastion’s death.
Also it is very easy to make a hero look overpowered by only saying the positives about that said hero and not considering/mentioning the downsides.
Also, if you go behind him when hes it sentry form, there is a box in the back that works as hit crit hit box.
Lol, every other hero is a counter for bastion. Thtas why you dont see him in the higher ranks.
If people dont know how to handel him, yes its a easy win.
He can easily be countered except when running pirate-ship, bunker isn’t that viable.
Though it’s not horrendously OP, only in lower rankings.
He’s easy to play and can completely destroy other users in lower rankings, though Average+ seems to not have this issue.
He doesn’t need a nerf, just a rework.
when fighting against bastion - try to take him down from the distance. his projectiles spread rate is high, which means the higher the distance the lower accuracy of his projectiles are. also, never stand against bastion. always move.
if you do so, you’ll very soon realize that he isn’t that OP 
we understand that you are quite new player here, therefore Ill tell you one more trick against nub bastions: jump on the top of the bastion (moira does it perfectly) and slowly and painfully kill him while he won’t reach you by any mean btw it works only in certain situations which you’ll figure yourself if you smart and dedicated to this dead game enough