How does Vulnerability interact with multiple instances of bonus damage?

Question

Suppose I have vulnerable 5 fire on a monster and I hit it with a basic melee attack. This melee attack comes with an extra 3 fire damage from Swordmage's Burning Blade, and an extra 1d4 fire damage due to a feature of the Malec-Keth Janissary paragon path.

Does this monster then suffer 5 bonus fire damage from its fire vulnerability, or 10 damage since it was hit by two different instances of fire damage?

Answer 1

I'm assuming you're talking about the Malec-Keth Janissary paragon path. Vulnerability only works once per instance of damage, because all the damage is happening at once, Vulnerability is only applied once.