I used to tank PuG's with my Pally back in the day and I had all the usual problems associated with the gig. DPS not caring about aggro, people complaining I'm moving too slow and pulling, etc.
The last few weeks I've been playing my DK and I'm ashamed to say I find myself becoming guilty of the same behavior. When I first began I would wait a few moments for the tank to get aggro before I started my dps and I would never use DnD due it's high threat.
Over time however, I've found myself becoming more and more reckless and yesterday while in a H PoS I actually said out loud to myself "Why is this tank moving so slow!" and proceeded to pull a mob. I have no regard for threat anymore and when I hear the aggro warning sound I just keep going. I even get some kind of perverted pride out of pulling a mob off the tank because it somehow means I "out did" the tank.
It's crazy how one's behavior changes when the shoe gets put on the other foot. Anyone else who used to tank and now does dps find themselves guilty of this? Maybe we could form a support group.
I've gone in the other direction, but I never lost my DPS-minded thinking, even after main-tanking all of 10ICC and most of 25, as well as most of the 10M HMs.
I think all players should start as DPS, before they switch to tanking or healing. And frankly, players need to try all *four* roles (counting melee and ranged as separate here, because they have to act different in raids) before they start trying to tell other players how to play.
People who tank and only tank get some level of elitism, thinking all other players must listen to them and follow their lead. You shouldn't have to tell people to follow you - if you're a good leader, whether it be in 5-mans or 25-mans or in BGs, they will follow you whether you want them to or not.
I will tell tanks how to play, and tell melee how to play, but for now I leave healers and ranged deeps to themselves. Until I get my Priest to max level anyways. :)
But if a tank is pulling too slow? I don't say a word, I just run ahead of them with my instant GW and pull the pack myself. That's what ShamRage is for!