Will bastion go back to recon mode if charged by D.va

Recently I was the defender you described. We didn't have a Bastion but we had a lot of Torbjorns.

What you are looking for is someone who can do a lot of splash damage from a good distance. While defending B my concerns were D'Va ult, Phara flanking from behind (generally anyone that can scale the left side where there isn't a path - had a Reaper few others come behind us a couple of times).

But the hero that annoyed us the most was a JunkRat. He was sitting nicely hidden in one of the rooms with a health pack and was spamming his primary fire. While doing so he'd bounce his balls on the walls and generally land them around us. He did quite a lot of damage and what probably saved was me getting really angry at him and going solo (even ulting to stay alive) and hunt him down.

More situational would be a well placed Hanzo ult, that would go trough the most entities.

TLDR: Junkrat behind a cover will do the job.

Here are some compositions that do NOT work: (But can be found in the answers bellow)

No, the ultimate cost for Call Mech was reduced to keep it in line to what it was before the global nerf. Patch notes here.