Lots of folks want to go go go and as a tank, while it's your job to set the pace so to speak, people will push it. Some don't get it until you wipe a bunch. When I was leveling DRK I had a healer and DPS berate me for not pulling wall to wall, despite my saying at the start I was the level of the instance and had slightly lower level gear. You just learn where your gear lines up, because as much as a healer can be skilled, they aren't going to want to spend an entire pull keeping you up and not wanting to DPS themselves. If you know you can't wall to wall pull, don't let them shove you into it (or you can try, I mean, maybe it'll be fun). If they get impatient and pull and die, that's on them. Lots of folks want to say "the healer can handle it!" but it also has to be you can handle it.