Yes, I'm aware of all that. Did you not read my entire post? My point is that the shitshow that ensues from the meta isn't relevant the overwhelming vast majority of the time, and where it is relevant, well, stance dancing is already a norm and required.
But outside of that niche (Savage raids and speed farming), it really isn't that relevant how much a tank optimizes their DPS relative to the stance (For clarity, I'm assuming their DPS and rotations are on point, but they play in tank stance more rather than less or vice versa. I'd even include a War that only goes Deliverance for Abandon usage). It's a DPS loss for the tank, but probably a gain for the healer anyways, so it's likey again, going to save a few minutes (And that probably a conservative estimate).
It's a strange phenomena that occurs in most meta centric games. Where issues are blown out of proportion or an unnecessary level of weight or importance is placed on people where that shouldn't be the case. Seriously, if we're talking about leaving a tank stance as a necessity, the tank will do it since it's raid tier content. If it's not a necessity, the DPS should be good enough to where a tank might cut the run time by 10% at most, which if they do, great, if not, then it's no worse than a Monk forgetting Fists of Fire or a BLM that absent-mindedly placed his Ley Line in imminent danger, only the latter should be criticized with some level of scrutiny since it's in the role title
Incidentally and on topic, I think tank stance shouldn't have the damage penalty, if only the cease this constant bickering over deeps deeps deeps.