Does the Executioner Assassin's Attack Finesse apply to all targets of that attack?

Question

Today, wizards released the Ninja guild option for the executioner assassin.

As one of its powers, it gets poisonous shuriken:

Target: One, two, or three creatures

Attack: Dexterity vs. AC

Hit: 1[W] damage.

Given that this is "Martial, Weapon" attack, does Attack Finesse apply to all targets or a single target:

In addition, once per turn you can deal 1d8 extra damage with a weapon attack using a one-handed weapon, a garrote, a blowgun, or a shortbow. The extra damage increases to 2d8 at 11th level and 3d8 at 21st level.

Answer 1

You only add your Attack Finesse damage to one target

Attack Finesse allows you to "deal extra damage with a weapon attack"

Each target of Poisoned Shuriken is attacked separately. The facts that they share a 1W damage roll, or that all 1, 2 or 3 attacks happen at the same time, as part of the same power, are of no consequence.

Answer 2

I asked @DaveTheGame (author of the article): "Awesome ninja article. Question: Does Finesse apply to all targets of shuriken?" , and he responded:

@DenubisX Only one of the targets, since it's 1/Rd.

While the compendium says it applies once per turn, the central point remains.