Hiya folks,
As prot/holy pally (yes i resisted the face roll spec), I can relate to what you say. From tanks that want to pull 5 packs at a time, whilst I was afk (and said i was), then dropping group cos 'the healer is !"$!"!', to raids (and even heroics) where dps stand in 'bad stuff' with no reguard for their own safety. That said on my main (dps) I do occasionally have the issue where i am not healed - the last time I said that I was told by healers I was and I was standing in bad stuff - thanks to recount it showed I didnt, and that i didnt receive any healing for over 18sec, and was basically ticked to death via enviroment damage. It goes both ways, with healers shouting at dps, and dps shouting at healers mostly. Oh and tbh I have not seen ANYONE link dps in heroics for a LONG time now - mostly people assume tanks n healers are in ICC 25 man (or 25man heroic) gear, and can now outthreat/outheal anything any heroic can throw at you.
As to dps specs tanking in heroics - I have one simple method to deal with them
1) ask if they want to change to their tanking gear
2) ask why they dont have tanking gear
3) vote kick
4) if vote kicking doesnt work - leave n requeue later

Obviously if the answer to 1 or 2 is something like 'I dont need it cos im 1337!!!!one111!!!', then it is straight to 3 or 4

Lastly if - as you say - you feel you are being made to carry the can due to others mistakes, then simply dont heal the twats. If they continually pull, say as a hunter, and dont even TRY to FD, then sure let them tank the mob, without heals. At least that way once he dies, the mob should return to the tank.