I don't really hate any dungeon to the point where I would instantly leave them.
Alwaysreap is annoying, Vault can suck when you are DPS (SO... MANY... INVINCIBILITY PHASES!), and Aurum Vale can be hard with some randoms, but all are doable.

Trials on the other hand... I lately tend to dodge Bismarck HM when I see that the issue is on the snakes DPS check, since that will not get fixed withing the allotted time. And when I get Steps in progress, where there are less than 6 people left, I also ditch that.