Except for the dungeons, you do the rest of the main scenario solo, so there is nobody to take over, and you can take all the time you want.
In the dungeons, where you have a party of other players, they'll usually slow down and give you a chance to see everything if you let them know that you're new. They may give you some pointers as well, letting you know what's coming up in the next boss fight, and so on. If, even knowing that it's your first time there, the level 50 players you were grouped with still take over and leave you behind, then you unfortunately got stuck with a rude bunch of jerks. That happens sometimes when you're playing with other people, especially if you get matched up randomly with those other people. Forming a group yourself by finding like-minded players to join you can improve your odds significantly.
