Oh, I thought you were playing devils advocate! Well that's how the fights in this game are designed Imoen, during those phases each player has a certain goal they need to meet for how much damage they do in a second. Its the contributions of the whole party needing to meet these checks which makes the magic happen. And unless you're dealing with naturally skilled players, you will eventually meet groups that cannot clear "DPS checks" under any circumstances. Simply because they aren't aware they're not currently using the skills in a way that would net them the damage they need to beat it.