How does Sigil of Safety actually work?

[Korror]

There is a new encounter power in Arcane Power from the swordmage Sigil Carver paragon path. One of my players is interested in taking this path but I have a rule question about its utility power that he and I are unable to answer.

The power runs something like this:
Sigil of Safety
Immediate Interrupt
Trigger: An attack hits an ally within 5 spaces
Target: Ally who was hit
Effect: You teleport the target to a space within 5 squares of you. The target gains a +4 bonus to all defenses against the triggering attack.

As I understand it, an interrupt always happens BEFORE the trigger so that example scenario looks like this: 1) Ally is hit by attack. 2) Swordmage uses power to teleport the ally out of range of the attack. 3) Attack fails. What makes me unsure about this is the second line of the effect part of the power. Why would they say that the ally gets a bonus against the attack if the attack is not going to resolve? There are other powers that have this kind of effect like transposing lunge. Have we been running them wrong the entire time? It could be that the +4 defenses is only used in the case where the ally is being attacked by a ranged power or a blast that you're unable to teleport him out of. I think this might be the only case where the +4 defences comes into play but I'm not sure. Does anyone have a frimer grasp on the rules and can answer my question?

 

[JasonZZ]

There is a new encounter power in Arcane Power from the swordmage Sigil Carver paragon path. One of my players is interested in taking this path but I have a rule question about its utility power that he and I are unable to answer.

The power runs something like this:
Sigil of Safety
Immediate Interrupt
Trigger: An attack hits an ally within 5 spaces
Target: Ally who was hit
Effect: You teleport the target to a space within 5 squares of you. The target gains a +4 bonus to all defenses against the triggering attack.

As I understand it, an interrupt always happens BEFORE the trigger so that example scenario looks like this: 1) Ally is hit by attack. 2) Swordmage uses power to teleport the ally out of range of the attack. 3) Attack fails. What makes me unsure about this is the second line of the effect part of the power. Why would they say that the ally gets a bonus against the attack if the attack is not going to resolve?
<snip>

The triggering attack fails if your ally is no longer a valid target (out of range, for example). If the target is still a valid target (still in range, for example), the defense bonus applies.

 

[mach1.9pants]

Yeah it works not just against melee range powers (but will be more effective!) but also if someone magic missiles him from a distance, maybe the 5 squares will move him out of range (and with monster powers you probably won't know the rage) maybe not. If it does.. attack fails, if it doesn't you get +4 to defences vs that attack. A nice power.