Now on to the topic (again).
For those curious to see a power that is listed as an attack, but which does not involve an attack roll, see for example:
Consecrated Ground (Cleric Attack 5)
Daily, Divine, Healing, Radiant, Zone
Standard Action, Close burst 1
Effect: The burst creates a zone of sanctified ground that lasts until the end of your next turn. You can move the origin square of the zone 3 squares as a move action. Enemies that start their turns within the zone take 1d6+your Charisma modifier radiant damage. You and any allies who are bloodied and start their turns within the zone regain hit points equal to 1+ your Charisma modifier.
Sustain Minor: The zone persists
And, as mentioned earlier:
DMG pg 54: Damage from an attack or from a source that doesn't require an attack roll (such as the paladin's divine challenge or the fighter's cleave) destroys a minion.
Cloud of Daggers does not
require an attack roll for it to deal damage.
So obviously you can have an attack that cannot involve a miss and which does deal damage and kills minions (Consecrated Ground), and a rule that says you can have a power deal damage to a mininion and as long as it doesn't require an attack roll for that damage the minion dies.
So why couldn't you have an attack power with two aspects: 1) An aspect that involves an attack roll and damage from that successful attack roll, 2) An aspect which deals damage in a manner that doesn't require an attack roll, and which still kills minions?
To put a different way, SadisticFishing, how would you word a power if you wanted it to do both of those things (have an aspect that requires an attack roll and which does not kill minions on a miss, and an aspect that does not require an attack roll and which does kill minions)?