For the Hunter's Achievement bags, they can be done in a raid. Can have folks all over the expansion hunting rares...helps a ton by getting kill credits across so many zones, plus keep the competition down for the rares, as it is a cooperative thing.
After requesting the video, I've seen both bags (28 slot and 40 slot) drop in EoK, and saw all of the rest of the bags from mission currency, collections, and hunters, cant wait to get more of them! :)