How do brutal and high crit weapons interact with non [W] damaging attack powers?

Question

At least two Swordmage powers are weapon powers, that deal fixed dice of damage rather than [W]s of damage.

• Spidersilk Slash ^ddi is a weapon power that deals 1d10 + int mod damage.

• Seed of Fire ^ddi is a weapon power that has a secondary attack that deals 2d6 + int mod damage.

Brutal reads:

When rolling the weapon’s damage, reroll...

So I don't think a brutal weapon would be of any use in this scenario, but I could be wrong.

High-crit reads:

A critical hit deals maximum weapon damage and an extra 1[W] at 1st–10th levels, an extra 2[W] at 11th–20th levels...

And here I am quite unclear as to what happens...

I can construct arguments for any of:

(examples at paragon tier, using a falchion - 2d4 damage, high crit)

• 8 damage (maximum weapon damage) + 4d4 (2[W])
• 10 / 12 damage (power damage, maxed) + 4d4 (2[W])
• 10 / 12 damage (power damage, maxed) + 0 (no extra [W]s when there are no [W]s)
• d10 / 2d6 damage (power damage, not maxed) + 4d4 (2[W])
• d10 / 2d6 damage (power damage, not maxed) + 0 (no extra [W]s when there are no [W]s)

Answer 1

For Brutal do not reroll any dice when using a power that does not grant weapon(W) damage. If it meant to apply to damage other than weapon damage it would be worded similarly to Critical Hit.

Critical Hit ^DDI states:

Maximum Damage: Rather than roll damage, determine the maximum damage you can roll with your attack. This is your critical damage.

This isn't tied specifically to weapon damage.

high-crit extra x[W] bonuses should be added for any critical hit. For the powers cited there is no base weapon damage, so maximizing it has no effect. However the definition of critical still applies.

For Spidersilk Slash, you would deal 10 + 2[W] + int (for paragon).