In most case I'm not familiar with the dungeon, and I cannot remember every possible mob path, ambush or patrol of every dungeon.
I'm also someone who likes to play it slow. Not at a snail pace, but I do not want to be rushed by someone else into doing things I don't feel comfortable with.
As I said, you can always ask if I could pull more, but you need to respect that the answer can be "No" sometimes.