tell that the people who low level DF and then proceed to pull .everything. even though the message that one or more players are new pops up.
while doing sastasha in 15 min is nice when you've already done it twice that day, it's annoying when you're on a brand new class you want to get used to - not forgetting to mention brand new players who may actually want to enjoy the dungeon for what it's worth (or the fact that those speed runner usually don't explain anything)
ps: I'm not talking about every lvl 50. earlier i had a super nice lvl 50 monk and paladin in my copperbell run who were fast - but still considering and making sure me and the other 'new person' could enjoy their run (watching cutscenes and so on)