Auspicious Mark: Not useful against saving throws?

[tivadar27]

So the Rage Power Auspicious Mark:
Benefit: The barbarian has been marked by the spirits, as indicated by an impressive tattoo, scar, or birthmark she possesses. Once per rage, as a swift action that costs 2 rounds of rage, the barbarian can call upon the spirits’ favor. Using auspicious mark grants her a +1d6 bonus on one d20 roll she has just made. She can call on the auspicious mark after seeing the result of the d20 roll.

The question I have, is I just noticed this is actually a *swift* action and not an *immediate* action to use. I believe this means you can't use it outside of your turn. Or in other words, if an enemy casts a spell on you that requires a save, you can't use Auspicious Mark to give you a bonus on the saving throw, because they presumably cast the spell on their turn. Is this the intent? Has there been a ruling/errata that I'm not familiar with?

[Cheapy]

Unless it's a save she makes on her turn, yea. Can't be used on Saves.

[RJGrady]

You can ready swift actions, if you needed to.