I think it's more that people are more likely to come to the forums to say something negative than to say something positive (in general), so the forums tend to be more negative than the actual game. Or at least a combination of that and negative experiences being more prominent in the mind, so they seem more frequent. You're right though, the majority of groups I've ran with in game are polite, and even when wiping, will follow the dungeon through to the end with little complaining.
The fear here, is one in every 8 runs may have a bad member in regular dungeon runs (higher frequencies if you're running Titan pugs, or CM.. bad member being defined as highly impatient, derogatory, and overall impolite, not just people who don't talk). So, that's 1 our of every 24 people. CT is 24 people.. so just by having a bigger pool of people, you're likely to run into those jerks more often. In addition to that you're mixing the folks that want to watch cutscenes, or do speed runs, or have practiced everything and perfected it, or who are just running to run it and don't really care. None of these groups can make a full pre-made, so they don't have a choice in being mixed with others. A lot of those personalities clash. Usually they avoid grouping together (for the most part) by doing pre-made runs. That isn't an option yet.
I understand the concerns, and understand where people are coming from in that regard. It won't keep me from the content once it keeps out.. I'm still going to try it, and hopefully all the worry is for nothing and everything is perfect. :)
A lot of it will be fixed at some point in the future when they actually allow full pre-made groups.
