Its mostly going to come from players who come from raiding guilds. For example, I can run HM LI in 15-20 minutes with my guild, never wipe etc, but when I pug it; it usually is an hour ordeal spent explaining mechanics and trying to teach someone how to play their class. It's not even elitism, its just that people from higher end guilds/groups end up expecting better and for the most part, pugs aren't close to the same quality as a good raiding guild.
On the same server as Opfotm and I completely agree. Our server, and I'm sure I'm generalizing here, has an incredible amount of amazingly awful healers. To elaborate: My brother and I are both raiders in our top raid group ( I'm a dps and he's a tank). Both of us are optimized 63 geared. I'm missing the Hazmat earpiece and he's missing the belt and bracers. Yet on multiple occasions, we've run with healers who can't seem to keep him alive, complain that he's too squishy to tank, and then quit on us when we just call them ****** at their job. Now, granted we might be very spoiled with the guildies we usually run with when it's 4 dps clearing LI HM (sorc off heals FTW), but we make sure to slow down some for pugs. There is no reason that a tank with 28k health should die on Malgus or Revan...or god forbid the trash at the start of boarding party. Last night he got accused of taking all the damage during some pull on Kaon and the healer was mad because he was used to " The damage being spread around more".
Since I can solo dps every single FP boss in this game; we don't have to worry about dps ruining runs for us. Far and away the most common thing we run into is crappy *** healers who have zero clue what to do.
As for the people complaining about dps pulling before your tank: all I have to say is that you have a crappy tank. Now, before you respond by trashing me; listen to my reasoning. I will be the first to admit that I pull quickly. I don't wait for the tank. If the tank has to keep up with me; I vote to kick him. The tank should be jumping to a group, agroing, and moving on. It's not your job to stay and try to kill the adds. That's why you have 2 dps...they kill stuff you don't. By the time you get to the second group of adds, your dps should be done and ready to come kill your group. They get to your group, you move on. Only time I will wait is when the healer is low on energy and force or high on heat. But again, If trash is causing your healer to go low on reasources, I'd probably vote to kick him as well. Flashpoints are meant to be fast. If you're in a flashpoint for the story; stop wasting the other 3 people's time and go solo it in SM.
EDIT: Also, just for full disclosure I am Mara. Rage spec for Flashpoints and Carnage for Ops. I can kill almost every single trash pull with one smash. Yet, I do the exact same thing one my Sorc, Powertech, Sniper, and Merc. My job is to kill stuff. I love dps and use flashpoints to refine gear and simple rotations. If tanks can't keep up; their fault not mine. Every single one of my toons has at minimum 61 BiS and I can kill most pulls with an AoE. Tanks literally have nothing to do except keep up