A thing to consider that's not strictly related to the difficulty of the fight itself. It's a major patch day. At least my FC saw a handful of returners who have been away from the game for a while and I assume that's common phenomenom across the servers. So you have players who might not have been playing a while, and might not have geared up to top. That already sets the bar up.

I was healing the fight yesterday. As for the incoming damage, most of it was rather manageable as long as people dodged what can be dodged. That of course is not the case half the time. Good amount of healer players have been for a while wishing for content where they actually need to heal, to use their whole toolkit for their primary purpose. That of course means that you have amount of healers who have been doing it just because it's been the easiest thing there is to do. Now they actually need to pay attention and work for it. Culture shocks all around. Give it a week and people have learned it well enough.