Does Damage Reduction (invulnerable rager) work with the Buffering Cap?

[icantfallasleep]

Buffering Cap wrote:

Once per day when struck by a critical hit, the wearer can spend an immediate action to convert the bonus damage of the critical hit into nonlethal damage. The cap has no effect if the wearer is immune to nonlethal damage.

Invulnerability (Ex) wrote:

At 2nd level, the invulnerable rager gains DR/— equal to half her barbarian level. This damage reduction is doubled against nonlethal damage.

How do these work together?

Assume a level 8 Barbarian, DR 4/- and DR 8/lethal. The buffering cap activates. Does the barbarian take 4 off the regular damage and 8 off the non-lethal damage?

Thanks for your help.

[icantfallasleep]

Bump. Anyone?

[Bronnwynn]

Your interpreation is correct.

[Avoron]

Actually, I think you would simply take 8 points off of the nonlethal damage. It's still one attack, so you only apply DR once.

Damage Reduction wrote:

If a creature has damage reduction from more than one source, the two forms of damage reduction do not stack. Instead, the creature gets the benefit of the best damage reduction in a given situation.

[Joesi]

It's hard for me to decide, because it's dealing both non-lethal and lethal damage. In my opinion that's reasonable to be treated as two separate sources of damage ("attacks") meaning applying the 4 DR on the lethal damage and the 8 DR on the non-lethal damage.