How does Blur stack with resistances?

The Blur passive skill states that it reduces damage taken by 17%.

Another answer stated that different classes of damage buffs stack multiplicatively, so I would suspect that also applies to damage reduction buffs. However, my character sheet shows this:

I do not, in fact, have complete immunity to poison damage like those numbers would imply.

How much damage reduction do I really have with Blur? And does the difficulty level negatively affect my resistances or just the amount of damage monsters do?

(If it's relevant, this screenshot was taken on Torment VI.)