Do the job you signed up for with the spec it requires.
And i would add with the skill to pull it off.
While I agree, most HM FP don't need a real tank or a real healer, I have done many on my shadow dps and have even done a few of those with a commando dps healing, but those were strictly guild/friend runs where I knew everyone's gear and skill. I would never run a random gueued as a tank.
Not one to instigate a vote kick, but if someone does for someone queuing out of spec, then I would go along with it.
Oh I still run a dps shadow, not switching to tank. Sorry, I have a healer as my main, I don't feel the need to play two support toons. I just don't have problems getting my daily/weekly done on her or the rest of my toons without resorting to making her a tank. I think because I can help others get the missions done on their other toons with my sawbones or operative. We just return the favor to each other.