[Disclaimer: I too know about the nature of this thread, but I want to give my insight anyway on the fight.]

I've seen people get knocked out by Tsukuyomi's ground moon phase from time to time, even after I have explained the mechanics to the new ones. Despite that, it still doesn't give you or anyone else an excuse to ignore this mechanic or say the instant death debuff is "new". The reason I say this is because because the "Doom" debuff has been seen in other mandatory MSQ duties - the first boss's room wide doom on "The Sunken Temple of Qarn" normal dungeon come to mind.

As far as most wipes on Castrum Fluminis goes, most of the party wipes occur during the Shiva-like spinning fans + Lunacy stack combo. Most people, especially first time healers, panic on dodging the fans and/or forget to stack with others to split the massive repeating damage. It domino effects into the party getting knocked out in about 10-20 seconds if players are unable to dodge and mitigate the stack effects as necessary.