Tank Balance

[Rbstr]

PLD DPS is lower because they have the shield (and, probably, the much more powerful "No Death" button).
They simply do take less physical damage, even if we can argue up and down about whether it matters or not (2.x it was certainly argued this is what made them the best, though I've never found it to be that valuable). That's worth some DPS in the dev's mind.

In addition, Authority is combo'd from Savage Blade instead of Riot Blade, which is inconsistent when compared to the other two tank classes.

This is a feature, not a problem, because Savage Blade has an enmity multiplier. It facilitates more Royal Authority when tanking and keeping hate.