Honestly I never had any issues with any dungeon. But that comes with being with a really nice guild full with levelheaded guys/girls who also are pretty skilled. So that makes everything smooth. But you can ofcourse notice a difference in terms of pugs you join. Grim Batol was indeed not that hard but the bosses had mechanics that would/could oneshot you or almost oneshot you but you needed to be 100% health. Atleast prenerf. And that made is pugunfriendly. So many people who just couldn't pay attention to anything but their castbars....died again and again... and then you wipe. I remember using every cooldown I had at every pack and boss until the instanced ended and sometimes that was just not enough. (healer)