Not that bards aren't powerful enough, but I've only seen one harp drop in NS--and it's really not worth picking up after about 10th level.
It could be a drop in the new DR area, an item you need goop for, or even make it its own post-epic quest (or all of the above!
). Maybe make it so you have to have 10, 20 or 30 levels of bard to use them for balance.
What to put on it? Ermm...I don't know...perhaps a unique power that increases your perform for a while (switching gear is kind of cheating anyway), or works like the new res pot from the Starfall area once per day, or...I'm running out of ideas...good thing I'm not a dev...
Mostly though, harps just aren't used at all and I was thinking it could be something else to add to NS--a bard's gotta have an instrument after all! Thanks.