The ENM system is currently broken so no amount of tanking will help with the fact that a single cure means a focused CON. Also, with the way that the mini-boss is "balanced," if the CON is focused, the CON gets 1 shotted. Those 6 parties most likely just got lucky because this is probably the most BS fight that I've ever seen in ANY game...and keep in mind, I solod Demon's Souls on NG++...