Bastion is fine the way he is. He's only OP in pub games where players funnel mindlessly into chokepoints over and over, repeatedly dying without changing class or utilizing flanking routes and high ground.
I'll be honest though, in such games I LOVE to defend as Bastion.
He's just boring as fuck.
PLAY OF THE GAME
3 people walk into stream of death, melt in 0.02 seconds