Can the Moga Power Pro be used as a USB controller?
No, there isn't. The official product website doesn't offer this as a feature, and I've tested with its little brother, the Moga Pro.

Incidentally, I've never noticed any lag or unresponsiveness when using a Moga Pro with a Nexus 10 on 4.2 or 4.4.2. Perhaps your lag can be blamed on a specific app you're running?