Let me put in another perspective, you're learning a new dungeon, now I'm not talking about YOU the elite awesome player who never messes up, I am talking about you the player who does dungeons with friends to learn it through and through and enjoy that. Now you hit a tough spot where a boss seems to be taking up some time and you can't quite figure out why...so you repeatedly attempt different things until BAM, something works, awesome! Now you've already been in the dungeon for 85 minutes, there's not enough time to finish it anymore and you have 2 bosses to go. Sad thing is you work tomorrow at 5am and while you love playing the game and would love to attempt the rest you just can't spare another 90 minutes to repeat the dungeon over.

That's my gripe, some people are learning, everyone learns at a different pace in different ways. I don't have the time to repeat a dungeon I enjoy playign with friends just because one or two of us couldn't quite figure it out. I like ot be in a dungeon and learn it and get as far as I can and let MYSELF be the timer, I'll decide when too much is enough.