theevilmonk's page

You are flanking the opponont, however any ranged attack you make will not have the +2 to attack (or any sneak attack for flanking) because of the wording of the flanking rules.

When making a melee attack, you get a +2 flanking bonus if your opponent is threatened by another enemy character or creature on its opposite border or opposite corner.

They get the bonus from you threatening them, however you get nothing for not making a melee attack

In my opinion damage dice would refer to the base damage (in this case with a greatsword 2d6) not the total number of dice rolled.
So base mythic vital strike should do x2 for 4d6+12 instead of 2d6+6, not 4d6+24.
I'd essentially consider it an automatic crit, that can still crit.
actually thats exactly what it is.

Extra note: Weapon damage dice for this case is described in the original vital strike feat which this is modifying

When you use the attack action, you can make one attack at your highest base attack bonus that deals additional damage. Roll the weapon’s damage dice for the attack twice and add the results together before adding bonuses from Strength, weapon abilities (such as flaming), precision-based damage, and other damage bonuses. These extra weapon damage dice are not multiplied on a critical hit, but are added to the total.