Do Story of the Vaal and Painseeker stack? That'd be insane!

And if so, is it additive or multiplicative?

Story of the Vaal has: "Hits with this weapon freeze and shock enemies as though dealing 150-200% more damage"

Painseeker gloves have: "Inflict non-damaging ailments as though dealing 100-200% more damage"

Looks multiplicative to me.

Max freeze and shock all the time seems nice and all, though not sure worth a weapon and gloves slot. IIRC bosses have some immunity time to freeze after being frozen to prevent a full stunlock.