I've played the first three missions from start to finish on online public, but none of the achievements unlocked. Anyone know what I need to do? Does the entire party have to stay together until the end? Thanks.
The co-op was frustrating. I did all the missions over and over again to get the achievements. If one player drops out, your hosed. I did finally get the achievements and my 1000 of 1000. Keep at it you'll get it eventually.