Tank stances should be reworked or removed but not for the bad players, but how poorly the stance scale with content, right now any proper tank will spend 99,99% of the fight in dps stance and 00,01% in tank stance for the pull, agro is not a problem if you are proper geared and know how to make a strong pull even with average gear.

The primary problem with tank stances are the 25% damage penalty (the penalty inself and the skills use in such stance make all tanks lose 25% of his maximun dps) and how clunky and punishing is use to it with DRK and PLD and the extra defense it's doesn't have any significative impac outside of mass pulling and even with that if you are good enough you can turn it off to make more dps.