Can a hero have multiple instances of vulnerable, each increasing damage done to that hero by 25%? I assumed you were either vulnerable or not vulnerable, based on how it is currently displayed. But the few places I have found where people discussed this online seem to think that it does.
For example, if Jaina takes Northern Exposure, and Sylvanas takes Cold Embrace, and then both use the corresponding ability on an enemy at the same time, does that enemy now take more damage than if just one ability that confers vulnerable was used?
If you can be made vulnerable multiple times, is the additional damage multiplicative (56.25% extra damage), or additive (50% extra damage)?