Marks apply a penalty when you make an attack that doesn't include the person/creature who marked you. It's resolved per attack, not per power usage.
In the case of Twin Strike, the power tells you to make 2 different attacks, 1 with your main and 1 with your offhand (or just 2 attacks in the case of the ranged version). For each of these attacks, look at who your target is. Is the target of your first attack the person who marked you? Yes, then no penalty. Target of the 2nd attack the person who marked you? No, then you suffer the penalty.
Area Blasts/bursts are different. You make 1 attack, that targets each creature in the area. If this single attack (that may or may not hit multiple creatures) includes the person who marked you, none of them suffer the penalty.
Now I'm curious how many people with Icy Rays or Eldritch Rain actually roll different damages for each target, instead of just rolling once and applying it to each target.
I don't know why people give these rules so much credit as to read de RAW.
This ruleset has consistently proved that it's RAW sucks. Big time.
I agree that the "damage roll" shortcut is the best interpretation of the RAW, but I also think it fails the RAI.
A mark encourages an enemy to attack you, but it doesn't force the enemy to attack only you. To avoid its effects, an enemy must include you in its attacks. If an enemy is making two attacks at effectively (flavor wise) the same time ("make two claw attacks"), I see no compelling flavor reason for that to be treated mechanically different from a close burst that is effectively a claw attack against each surrounding enemy.I disagree. I think the point of the mark ability is that you want the enemy to attack you. If that happens to mean throwing a fireball big enough to hit you and your friends, then so be it. If that means spinning around rapidly hitting everyone, then so be it.
But any power that makes "two attacks" are specifically targeted attacks and the enemy is choosing not to hit you with the second one.
But any power that makes "two attacks" are specifically targeted attacks and the enemy is choosing not to hit you with the second one.