^ That's a shame. I was hoping they might make an appearance. Maybe future dlc. I can't imagine they'd bring them only to MP.
you are a braver man than I, unless I've had a great team, taking down the collectors on bronze has been a challenge. Got sandwiched between 2 Praetorians, at least 3 Scions and a lot of troopers last night. Plus, I had to carry a package to the landing zone. Went through all my medigel in less than a minute and failed the mission.