What bugs (excluding class balancing, pathing, and the sound engine of shitness) are still left unfixed from LDoN? Remember that UI updates are happening all the time, so you can't blame that on an expansion per say, as things get added all the time.
Saying an encounter is impossible is not a bug, that's SOE not knowing how to design said encounter. Class Balancing has been a grief since DAY ONE OF EVERQUEST. Wah the necros are too powerful, wah this class is too powerful, wah the enchanters, wah the Shamans are too wimpy, wah wah wah. That is something that will not go away, no matter what. You cannot please everyone. SOE used to be on the hard line stance of having their "Vision"TM, and have clawed back from that and given what a lot of the classes have wanted. Yes there are still major issues with the class balancing, and I'm not denying that. I played a monk, and going from superman to mediocre with one nerf kind of stung, but I wasn't surprised it was coming.
People complain constantly about zones being overcrowded, about content not being there, or old content should be revamped. I think old content should be, however SOE never laid claims that they would revamp a zone at a later date. I like it when they have, and I know they've screwed up their rollout of some of the revamps (Frontier Mountains not being updated when Drolga was, for the Angry goblin as an example).
Bugs are to be expected with each release and patch of something. SOE has improved greatly in their rollouts of new expansions. LDoN was what I would consider one of the best rollouts to date with minimal needless downtime. Their patch time have improved quite a bit from the 12 hours of doom down to the 2 to 5 hours they actually say. There are times where they fumble, but it's nothing like before.
Itemization is another complaint with each new expansion. Again this is NOT a bug. This is SOE being too braindead to understand fundamental balancing/design flaws.
Dup bugs and EXP abuse bugs have been around forever. People are constantly finding ways to circumvent the rules. SOE does address fixing those bugs, but if you notice their lack of Customer Service, and their want of the almighty dollar, has staved them off from going on the rampage with suspensions and bannings. The latest EXP abuse bug with charming is a classic example of it. People have been freely admiting to abusing it, however they had no repercussions happen to them.
As for your comment about expansions between MMO and MP games, I never said they were the same, however you do miss out on feature sets that aren't provided to you otherwise. Classic Example - NWN you need to have Undertides to become an Assassin, if you buy Hoardes, you still do not get access to this Prestige class. How is that any different? Oh wait, it's nots.
Now to address addiction - Personally I don't find a game where you do the same thing repeatedly to be addicting. Tradeskills are about as entertaining as getting a root canal in my books, but to each their own in what they find fun. The enjoyment for me was in pulling, exploring, seeing new areas. Seeing how much I could haul in to the raid force in a pull without causing a wipe, and cackling gleefully when I did cause one because I got to hear my GM yelling at everyone.
As for griefers in a game (what you experienced with that guy cussing you out). You find that in any game.
PS - MY EQ Days aren't 'old' considering I cancelled my account in mid December. Also, if you're going to insult me in a round about way by saying I don't have a clue, at least have the balls to say it straight out.