I remember having an argument with a rogue about this on his disc priest as apparently he was monitoring what our very polite druid tank was doing closely as well as knowing priests.
Druid said he was wrong, I said it was wrong, yet he kept going. In the end we just killed him, pugged a newly dinged hunter for free badges and carried on. Rapture tanks aside from paladins like so if it's a pallie and they seem to be fine I switch to renew otherwise I just bounce in and holy nova.
It's amusing when dps know more about tanking and healing roles than we do