I'm guessing you're playing either mystery heros or a version of free for all in arcade. In those type of games bastion is extremely OP as the enemy can't always pick a hard counter for him like a reaper.
Not knocking your bastion play, but to get a better idea I'd have to see you in a real match I suppose, playing alongside a team that is picked. From what I did see of your bastion play, you were in turret mode for too long, but again, in a regular play mode you would have to be more mobile. Successful bastions nowadays are rarely in turret form unless well protected, but even then the enemy team is devising a plan to take you out.
So yeah, only suggestions I can give you is practice moving around regular, then dropping into turret, then moving, dropping etc etc. A good bastion won't stay in turret very long, always looking to reposition and then when the time is right get down into turret, back up etc etc.
Hope that makes sense, I'd be happy to help if you were wanting some pointers anyways. I enjoy bastion, but he's not the same bastion he used to be. Less powerful from distances for sure (WAY LESS powerful) so it is important for him to be up closer to the frontline breaking shields and tearing apart squishy's.