Well, thanks to PoisonPinkFluff and crlhle, I'm now halfway through the campaign on Legendary. I've still got to go through Tayari Plaza, Uplift Reserve, Kizingo Blvd., Data Hive, and Coastal Highway. I guess not technically halfway, then, but whatever.
Still looking for folks to fill out the rest, and of course I'm more than willing to play through missions I've already done to help others out.