[RPG] Brutal Weapon Property and the Bugbear’s Oversized Weapons ability

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).

1. No the extra 2d6 are not brutal. Dice granted via a magic weapon are not [W] damage, but extra dice.
2. Yes, the extra dice granted by high-crit are brutal as they are specifically [W] damage.

From the Adventurer's Vault FAQ

I am wielding a magic weapon with brutal 2. If I roll a critical hit, do I get to re-roll 1s and 2s when I roll for the bonus damage?

No, the brutal weapon trait only applies to rolls for normal weapon damage, signified by [W]. The bonus damage for critical hits does not qualify for this. However, because high crit adds a [W] roll (or 2[W] or 3[W] depending on your level), you would get to re-roll any 1s or 2s.