Honestly I disagree with most of these suggestions. I understand wanting penalties for those who leave early but a blanket penalty just does not work. Since it's not appropriate to remove someone from the dungeon for being brain dead (which I've been finding more and more of lately), leaving the dungeon of my own volition is sometimes my only option. Sitting with a group of people and wiping on the same boss for hours is not my idea of fun. I'm all for helping others, but some people refuse to put in the time and effort to not waste other players time.
For example, I needed Sunken Temple the other day to complete my atma book. So I cued up on my tank and got into the dungeon. The "new player" think popped up. So I pulled like normal and announced mechanics that were pertinent to each pull or the boss. After we wiped at the first boss (half the party died to the first doom because they didn't understand the mechanic). We ran back and I kindly asked. If you are new to the dungeon please speak up and ask questions so we can explain the fight and help you. One of the players said, "I'm good been here before." complete silence from the other players. SO I explained again in more detail and we wiped immediately again. Same two players died. I asked them why they kept dying and they said, "Idk its hard" ...I asked what was hard and they said they kept dying and couldn't figure out what was hitting them. It was almost as if they had just completely ignored all my explanations. I then suggested that they should watch a video of the fight to help them learn the mechanics and they got pissed off. Really? you expect me to take the time to carry your lazy a$$ through the dungeon when your not willing to take the time to learn it.
At this point I just left the dungeon. I've got better more important things to do than to babysit people who should just go ahead and delete their account.