Here is my response from that thread:
I would say a complete set would be Base Game, Caverns of Roxor, Von Drak Manor and then the individual heroes/mini-bossesthem which are Succubus Vandella, Herald of Vulcanis, Captain R, Kaelly the Nether Strider, Nyan Nyan and Candy & Cola.
The Rock Top Gang and Fireflow Denizens are optional imo. If you wanted to play 5 hero games completely with Caverns stuff then you would need Rock Top/Fireflow. They also come with unique treasure cards but I think we're likely to get these with the new sets coming with Forgotten King. If you absolutely have to have everything then you might get them but I don't think it's essential.