I think the problem in this instance is communication. When the dungeon starts, everyone should communicate first. I don't mind speed runs, but do you know when i hate speed runs? when the dungeon starts and someone just takes off without saying anything and as soon as they pull a mob, a message pops up from someone else in the party saying they are new or they are lvling a new alt, so they want to fight as many mobs as they can. All it takes is communication. If the tank wants to do speed run, then say so before you pull a mob. If you want to fight all mobs or are learning the dungeon, say something so others can know.

I think SE should add something in for both types of players. Maybe like a weekly dungeon log similar to hunting log. Either have to kill certain mobs in dungeon for exp. boost or meet certain requirements in dungeons for exp bonus. For ex. complete dungeon in certain amount of time, receive bonus exp or tomes or allied seals. Or hunt certain mobs in dungeon for extra seals, etc. If SE adds these things to old dungeons, it will help make the experience less stressful for people on both sides. Im gonna pitch this to them.