To do any instance with 5 shamans you need to outgear the instance most of the time. It's much harder that it looks on the youtube videos. I have tried it to do normal instances with 5 shamans and even normal you need to outgear it. Heroics are possible once you get full pvp gear and epic items. But once you have these, why would you want to do heroics? I am now running 4 shamans + 1DK and I can do any instances easily with the gear that is expected for these instance.