Dodge (Mythic)
The bonus to AC from Dodge increases by 1. As an immediate action, you can expend one use of mythic power to grant yourself an additional +10 dodge bonus to AC against one attack.
How does this feat work when a fighter with this feat is using it against an attacker? Does the player need to declare that he will use the mythic power to grant additional +10 dodge bonus before the result of the attacking creature is revealed? Can he simply declare it after the DM reveals the result of the attack?
For example. A 9th level fighter has 27 AC. He is attacked by a giant that has +19 attack. The DM rolls the dice and he gets a 15. 15+19 adds up to 34. The fighter would be normally hit by the attack. Can he declare he will use his immediate action to use Dodge (Mythic) after the DM reveals he would normally hit the character?