I understand what OP is trying to say, but, you need to start from bad DPS, as example, 400 DPS Bard in 250 average ilvl is unnaceptable (no deaths). (This was a real example, that my friend told me not too long ago, he was furious)
At least, as i know, for top players parsers help greatly to identify those guys.

On the case: i found myself running a lot without tank stance, no problems there if you also know your teammates (aka look at them before the start).

Example: If you have a ilvl 270 BLM in your party, you better pull tank stance ON almost all the time if you're undergeared tank.