Samir argues that the word
attack in following quote (PHB 269) refers to
Attack: line in power.
Making an Attack
All attacks follow same basic process:
1. Choose the attack you'll use. Each attack has an attack type.
2. Choose targets for the attack (page 272). Each target must be within range (page 273). Check whether you can see and target your enemies (page 273).
3. Make an attack roll (page 273)
4. Compare your attack roll to target's defense (page 274) to determine whether you hit or miss.
5. Deal damage and apply other effects (page 276)
Which would resolve to following line in power
Attack: Strength vs. AC (melee; main weapon and off-hand weapon) or Dexterity vs. AC (ranged), two attacks
Personally I think it can only mean whole power used for attack, which in this case would resolve to following parts:
Twin Strike
At-Will
Martial,
Weapon
Standard Action Melee or Ranged weapon
This interpretation has added bonus of fulfilling the "Each attack has an attack type." portion of the rule quote above,
Melee or
Ranged in this case.
It's also far more logical way to parse powers.
I'll give you rundown how Twin Strike (quoted below) should be read/resolved in my opinion as per PHB 269:
Twin Strike
At-Will Martial,
Weapon
Standard Action Melee or Ranged weapon
Requirement: You must be wielding two melee weapons or a ranged weapon.
Targets: One or two creatures
Attack: Strength vs. AC (melee; main weapon and off-hand weapon) or Dexterity vs. AC (ranged), two attacks
Hit: 1[W] damage per attack.
Increase damage to 2[W] at 21st level.
1. Choose the attack you'll use. Each attack has an attack type.
Twin Strike
At-Will Martial,
Weapon
Standard Action Melee or Ranged weapon
Requirement: You must be wielding two melee weapons or a ranged weapon.
2. Choose targets for the attack (page 272). Each target must be within range (page 273). Check whether you can see and target your enemies (page 273).
Targets: One or two creatures
3. Make an attack roll (page 273)
Attack: Strength vs. AC (melee; main weapon and off-hand weapon) or Dexterity vs. AC (ranged), two attacks
4. Compare your attack roll to target's defense (page 274) to determine whether you hit or miss.
Technically the vs. AC part of the
Attack: line is resolved here.
5. Deal damage and apply other effects (page 276)
Hit: 1[W] damage per attack.
Increase damage to 2[W] at 21st level.
In-play example with Ranger:
1. Ranger decides to use Twin Strike. (Requirements for power are fullfilled.)
2a. Ranger picks his targets, Orc A and Orc B. (Targets are valid.)
2b. Ranger picks Orc A as his only target. (Target is valid)
3. Ranger makes two attack rolls. (IMO this is what the "two attacks" in Twin Strike really means). His total is 21 for first roll (Orc A) and 19 for second roll (a:Orc B, b: Orc A again)
4. Poor Orcs have only AC of 18, both attacks hit.
5. Ranger rolls damage separately for attacks. Damage from both attacks is taken simultaneusly.