I would say it was quite challenging, though if the mechanics were done PERFECTLY it wasn't toooo bad (i was just dps so I probably have some bias) however I feel like it could gain a health buff anyways, like 30-50k so that it would take either a perfect group (probably what we had + a druid instead of a crus) or better gear from the other two bosses to increase the group dps/mana pools enough.
The damage seemed fine since it seemed like a mechanic oriented fight anyways (which in my mind shouldn't do THAT much damage unless you fuck up then you're punished hard).
The difficulty seems in the end to lie in the sheer mana drain on the healers which I think is nice.