Hmm... I really get the feeling that you're doing something wrong.... I'd be happy to play through the mission in a team.
In this case, it's not a matter of doing something wrong. The mission is already wrong. The trick is to find a way to overcome the wrongness of the mission. I think it's safe to say that the average player trying it solo isn't going to find a way to do that without a great amount of effort and/or a great amount of luck.