Rogue daily power Profit from Weakness

Question

I'm building an Rogue duelist and have a question about the lvl 9 daily: Profit from Weakness

Profit from Weakness

You step aside as the enemy’s attack sweeps toward you. You then slide your blade into a place where the foe is vulnerable.

Daily * Martial, Rattling, Weapon
Immediate Interrupt * Melee 1

Requirement: You must be wielding a light blade.
Trigger: An enemy adjacent to you hits you with a melee attack
Effect: You gain a +4 bonus to all defenses against the attack. The triggering enemy grants combat advantage to you until the end of your next turn.
Target: The triggering enemy
Attack: Dexterity vs. Reflex
Hit: 2[W] + Dexterity modifier damage.
Miss: Half damage.
Effect: You knock the target prone.

So I have a +4 bonus to all defenses but now I wonder, does the enemy also gets a -2 to attack for attacking while prone? Because I interrupted his attack and knocked him prone before his attack hits me, but that doesn't seem right.

So I would like an explanation: does he get the -2 penalty or not, and why?

Answer 1

Immediate Interrupts occur before the triggering action.

Interrupts: An immediate interrupt jumps in when its trigger occurs, taking place before the trigger finishes. If an interrupt invalidates a triggering action, the triggering action is lost.

Example: An enemy makes a melee attack against Keira the rogue, but Keira uses a power that lets her shift away as an immediate interrupt. If the enemy can no longer reach her, its attack action is lost. Similarly, Albanon the wizard might use shield in response to being hit and turn that hit into a miss, or Keira might use the immediate interrupt heroic escape to evade an enemy’s attack before it can deal damage.

— Player's Handbook, page(s) 268, Rules Compendium, page(s) 195; also available in the DDI Compendium.

The enemy is at -2* to-hit and your defenses are +4

Thus everything in the power occurs before the hit actually lands. The attack you make is part of the same interrupt as the other half of the power and so it resolved before the original triggering action.

The enemy is knocked prone by the power's final effect line.

*If your rogue is trained in intimidate then the enemy is at a -4 to-hit because the prone condition's penalty stacks with rattling.

Rattling

If a creature has training in Intimidate and deals damage with a power that has the rattling keyword, the target takes a -2 penalty to attack rolls until the end of the user’s next turn. A target that is immune to fear is not subject to this penalty.

An effective total of -8 to a single attack is quite reasonable for a daily power.