The problem with the Trial was that youre asking a random group of people over the internet to cooperate. That usually almost never ends well. With the boss having less HP than before, you can still have a chance of winning even if you miss a large cannon shot. I'm all for difficult gameplay, but the way it was before was "Oh you missed a shot? Guess what, youre screwed. Now please wait patiently for the boss to slowly walk towards your inevitable defeat." And with no way to reset the trial to a checkpoint a loss can be incredibly irritating just to go back to the one spot you screwed up on. "Missed that vital canon shot at the very end?" Hope you enjoy 10 more minutes of doing the exact same thing again.

Take that as you will. But remember, when youre asking random people to cooperate, you have to take into account that almost no one wants to step up and give out orders and some people just refuse to cooperate even if it means a win for the team. Were humans. Were a**holes by default.