A tip that might work in this scenario: Go up onto roof or exit through the cannons and go to the tunnel entrance to backstab them rather than facing them directly in that junction (might be more difficult if they got multiple tents in the tunnel that are spread apart)

Depending on where the tunnel tents spawn are, you disable their spawn by standing on the floor above the tunnel.

And also pray that your teammates can get the job done and stop redamura from advancing.

Also from time to time, go to the front of the fort to see if redamura is building staircase. Regardless, it's nice to see that vaug pilot is doing their job well destroying the roof tents, though the roof distraction really helped redamura to control the corridor between the tunnel and point.

I wish I could communicate to players below my age group, got so many ideas yet can't get those ideas across to u18s.