I only play Mercenaries but the maps are the only DLC I've got...and usually with randoms.
I also play the occasional Agent Hunt and in this case, it's actually a good thing most of the veterans have moved onto Revelations. Less likelihood of encountering a camper.
I play Campaign online if an event calls for it and I usually help out someone if they're playing a chapter the event calls for. Online makes it less tedious. I'd like to go for a No Hope run with someone but no one comes in and if someone does, they usually leave when it gets too difficult.