Since when have tanks ever cared about what a healer is doing except to yell out "HEALZ!' After pulling the entire room after the healer said "OOM Drinking".
I kid, not all tanks are like that, just the majority you run into. They generally don't care that they're stressing their healer as long as they don't die.

I disagree. The basic intention, abused as it would end up, is for a dps warrior that happens to have alot of high lvl (DS or 378 maybe) to just switch stance, gear, and tank an old heroic. Possibly on the high end, a tank with higher than RF DS gear tanking a new heroic.

I would argue this would be no worse than a prot spec tank in gear the instance was designed for. (not min ilvl, the intended gear lvl for entering tanks,333 for old heroics, 346 for trolls, 353 for new ones)

If the argument is that a tank spec tank in appropriate gear for what the dungeon is tuned for should stay away, then that's just being whinny due to a slightly slower dungeon and isn't worthy of consideration. Any healer should be queueing with the expectation(myself included on my two main healers) of healing a tank geared to the minimums, anything above that is just a bonus. A crit immune dps tank (the ones talked about in the post, that don't exist outside of sidespec'd kitty droods right now) in appropriate gear + 30 to 50 ilvls ahead should be quite out in front of a tank spec tank in min gear(Tanking old heroics in 359-378, or new stuff in RF or normal DS stuff).

As someone who's leveled entirely by healing, and healing oh so many pug tanks, this really resonates with me. I know you want to do what's fun for you. But spending ages trying desperetly to heal you while somehow not letting everyone else die as well, is not my idea of fun either. Everyone has to start somewhere, but be responsible with it, as you have everyone else's 40 minutes of fun in your hands and at your mercy as well.