The beta battle is just a small skirmish. Don’t be surprised if the large scale sieges are broken up into smaller instanced sections with set goals.
The story will unfold as is. It’s already happened. It won’t be changed, so the sieges will happen. The only question will be the scale of our involvement.
Also, most of what we saw in the trailers are prerendered cut scenes. Even in the large battles, we only see some small scale 1v3 with things happening in the background.