Just. Don't. Piss. Off. The. Tank.
I will be the first to admit that tanks in random groups can be jerks sometimes, especially since their queue times are zero and some of them take this as a license to be assholes. Most tanks I've run with (as well as most dps/healers) are nice, regular folks. Generally, people in randoms are well-behaved, in my experience, because they just want to finish the dungeon without too much drama.
I like to think that I'm a nice and accommodating group member. I always try to keep things civil and I don't want to upset anyone if I can help it. Now of course, when I'm running as a dps I prefer to keep my trap shut or else I might find myself booted but when I run as a healer I'm a lot more vocal and when I'm tanking, you better not fsck with me BIATCH!
When I tank, I have something akin to a "zero tolerance" policy or perhaps a "two strikes" policy. If you do something stupid, I'll warn you but if you do the same dumb thing again, you're on your own.
The other night I was running a random Scarlet Monastery Cathedral dungeon. As soon as I got in I noticed that the mobs were gleefully coming at me without being aggroed by me at all. After a couple of minutes I realized that someone was pulling them. It was the damn healer, of all people.
Fine, I decided to go with it, grabbing aggro and dispatching the mobs. The healer did a good job keeping me up but then he went and pulled more and yet more mobs. When we got to the actual cathedral he rushed in and pulled about half of the mobs. We survived and I said "Thanks for pulling for me". This remark got ignored of course.
Then he told me to pull the boss even though the room wasn't cleared. I decided to clear the room instead. What did the healer do? You guessed it! He pulled the boss. So what happens in Cathedral when you pull the boss and the place hasn't been cleared? All the remaining mobs, regardless if they are out of range or LOS, or in rooms, swarm you.
Since the healer felt that way, I decided to spare myself the trouble and declined to tank that nasty pull. I'm sure that if I had cooperated we might have been able to pull it off. The reason I didn't is because it creates a precedent and sends a signal to that healer and perhaps to other members of the group that it's ok to pull mobs whenever you feel like it, disregarding what the tank may feel about the situation.
So I did the only sensible thing, which is to shift to kitty and haul my ass out of the dungeon, while the group was being raped. Since I didn't have any aggro from the dozen mobs + boss, I didn't have any trouble running to the exit. On my way I typed "Have fun tanking". Maybe leaving like that wasn't fair to the rest of the group and I really feel for them but it was the healer's fault through and through.
It turns out that I'm a very good tank (so far) on my druid. I've received compliments on numerous occasions in regards to my tanking prowess. I don't make a habit of leaving groups at the drop of a hat despite the fact that my queues are instant. I respect others but in return I demand a modicum of respect, especially when I'm tanking. That healer had it coming and the group was doomed anyway under his... healership.
I've had another guy a couple of nights ago, dps this time, who was in a hurry or something because he kept urging me to pull lots of mobs. I ignored him and did my own thing. I'm not usually comfortable with pulling tons of mobs in random dungeons because healers are sometimes very good, sometimes bad but most often average and I go by the mantra "better it takes a couple of minutes longer than to wipe". Besides, successfully fighting large numbers of mobs also depends a lot on how efficient the dps is at AOE-ing them down.
So please, dear folks, whatever your role, give the tank some respect and in return you will receive it (unless the tank is a total dick in which case he's not worth a dry turd anyway). Unless the tank specifically requests it, DO NOT PULL under any circumstance. The tank sets the pace, not the dps and not the healer. If you don't like it, that's too bad, put up or shut up. If you really got the itch to go at your own pace I suggest trying a tanking class or spec. Let's see how you like it when others are trying to run the show for you.