As this is a topic for general questions, with lower level players clearly in mind, may I add one of my own please, hopefully without being accused of hijacking the topic? Incidentally, I found Enkidoh's response really useful, thanks for both that and the OP's questions that triggered it!

I am by nature a soloer in MMOs, as I like to take things at my own pace. To what extent are group-based dungeons required in the game, how tolerant are most groups of those not used to either the dungeons or the grouping needed for them, and how do people see them working out once the initial rush is over and most players are at endgame (a concept anathema to me, I play for the journey rather than the destination), is it generally thought that dungeon groups at lower levels will be difficult to find once most players have moved on to the higher level stuff?