It is possible to do the team quest in Vulture's Vale alone - but you need a lot of time. This video is not sped up, it's real-time.
I had some problems with my recording software, recording 45 minutes of stuff didn't work so well. ;) So I had to cut out the beginning (the quest-giving) and at the end the walk home after the talk with Anya. And near the end I died and hat to revive in the fortress, so I had to walk to the battlefield again - I cut this walk too, it's useless waste of time. 01.02.2015