It´s actually a design-issue SE makes every expansion.

First of all, the new trial is no hard. It´s just because ppl don´t know what´s coming and some casuals need more than 1 try to get used to them. Why? Because the game NEVER forced them to learn and to get an eye for certain mechanics. If ppl stop standing is those long-cast aoe´s, the healers wouldn´t have to do much beside the doom-cast.
So far SE´s bad design choice is, that the fights are not really challenging or complex, but rely on the 8th player. In normal mode it´s not a big deal, but in expert or savage? One guy miss to play a mechanic and it´s a wipe. Players getting punished for taking someone "not so good" with them. The carry possibilities, if the majority knows what to do, are not really a thing. And given to the fact, that the most content never force any input from any player and MSQ even comes up with a "easier please" button or Echo, the most ppl gonna be noobs all their lifes and wipe way too much parties with their incompetence.