Most times I run a dungeon without a premade, the time is increased by at least 50% than if I had gone with a premade.
About half the time I run trial roulette without a premade, we wipe at least once. If it's Ramuh hm, I go in expecting more than one wipe.
Again, this happens about half the time I run it without a premade.
I've seen it multiple times. Although I don't condone harassment, the victim did bring it upon themselves in each of these cases.