Having usually played DPS roles (even on my 'healers) I decided myself to switch to a Tank class and build so I rolled a Vanguard. I was in an easy heroic and the sent kept leaping into the fight before I had grabbed full agro from all the mobs of the groups. I repeatedly told him to WAIT until all the mobs were on me and I had triggered my very visible explosive type AOE to let the group know they could attack now.
Never listened and then complained that I was a bad tank because he kept getting agro, when he would leap in before I HAD agro. Yeah. I ejected him. As a Vanguard I have lots of agro gaining tools. There is no excuse for a group member not to wait until I signal the attack when I have CLEARLY stated what that signal was. So OP, I feel your pain. Running a pure Tank class has made me a significantly better DPS player on my other characters because I know now what to look out for and when to throttle back my attacks so the Tank can maintain agro.
The only time I ignore that advice is if a mob has pealed off and goes after the healer, and then I'll do everything I can to change it's agro focus.
I prefer to think that common group etiquette is well known, but Its the context of the situation that is more important. An overgeared group has no need for a tank in a HM flashpoint, and it is often just easier to let the dps burn everything down, and the healer heal as needed.
Nobody should be having a go at a tank not holding agro in a hardmode flashpoint with everyone burning through in 61's. If a healer in 61's can't keep up dps in a boarding party, thats the healers problem, not the tanks or dps.
These conflicts seem to be focused around the group finder, where you have overgeared players blended with players in gear that the content is balanced for. In a situation where either the healer or the dps are in tionese, then the pace of the flashpoint should be set to accomodate them.