I have to ask, does this experience only occur in high level dungeons? (50)? As, so far, I've not come across this sort of behavior in any Brayflox and under dungeons (many of which I've run multiple times for aesthetic armor pieces). Most people I've run into have been extremely helpful: explaining mechanics to new players, helping tanks out and reassuring newer and less experienced tanks when they feel they're not doing as good of a job as they could be. It's completely different from my WoW experience, wherein (a low level dungeon), people would blow up at each other and toss out slurs, profanity and insults like no tomorrow. (So, I wouldn't say it's worse?)
While it's not a pleasant thing that this sort of behavior is occurring, the most I can think of is to report players for harrassment if they're acting insultingly towards others/yourself in the run, using slurs, instigating fights and antagonizing people. Just them going AFK, or initiating cutscenes, isn't enough to report the player, but blacklisting the individual might help? If it doesn't, why not try to find a friendly and helpful LS and FC to group and run with? While it doesn't fix the overlying issues, it will at least improve your experience within the game (and the community may take a shift after the free period expires, or a bit after the initial drop off in population -- a lot of communities for MMO's I've been a part of get huge initial flack, but they tend to pull themselves together after a few months).
It's sad to see this sort of behavior persist, but I fully intend to keep playing this game (need to re-learn it for my PS3/4, as my desktop just exploded) and I imagine that trying to be that nice, respectable and helpful player (regardless of the interaction within a dungeon run) could help the community as, to a degree, it might help negate the apparently rampant issue with people abusing game mechanics or acting immaturely.
Just my thoughts :I