Definitely an improvement (though ultimately, I'd like to see the removal of tank stances, at least from PLD and DRK, with mitigation being more active / interactive)
If stances are to exist though, a few things to add:
1. Removal of 'enmity' combo (or at least reworked to be frequently useful*), with 'extra enmity' from basic attacks** instead tied to stance... not sure how this would work prior to level 30, maybe being in 'DPS stance' removes the enmity modifier (as opposed to 'tank stance' adding it).
2. PLD Shield Oath also boosts Bulwark block rate to +80%, making block rate 100% while Bulwark is active.
* Would also be nice if each tank was a bit different in their combos (as opposed to them always having 3-part Enmity + 3-part DPS).
** By 'basic attacks' I mean Rage of Halone, Power Slash, Butchers Block, etc. … Flash, Shield Lob, Unleash, Unmend, Overpower, Tomahawk, etc. would always have 'increased enmity' regardless of stance.