The Novice Power feat reads
You can swap one encounter attack power you know for one encounter attack power of the same level or lower from the class you multiclassed into.
Note: If you have no encounter attack powers, this feat grants no benefit to you.
I have a Slayer multiclassed into Barbarian with the Draeven Marauder paragon path. As a Slayer the only encounter powers he has is multiple uses of Power Strike, but power strike has no level, and so cannot be swapped out with Novice Power.
Draeven Marauder however provides a level 11 encounter attack power, and presumably should be swappable but the character builder does not let me.
What is correct here?
Rules Compendium, page 90:
Also, Player's Handbook, page 209