I think the main thing is you need to find 5 people who can control their 5 characters pretty well, are all interested in pushing PvE. I think maybe if you found those 4-5 people with 4-5 chars, you'd still need to rely on a few normal people, because in the end, people get bored, have life to attend to or just cant show up that night. 1 person can't log on? Your 5 people short.