When I've been stuck in shit like this, I just put in the extra effort and turn the entire assignment out myself. I submit it to the prof as such as well, giving no credit to the 'group'.
It sucks, I know...your time is already pressed as it is. But it's the only solution. No matter what you try, you're going to get shit from these guys. Even if you can get them to participate, you're going to get sub-standard work.
