There's a named Oathbreaker that can pop in at least 2 places normally occupied by spirits at Amon Amrun in the Fields of Fornost that can drop ruby shards. The main location is in the gazebo in the center of the ruins, and the second is next to a crumbled wall to the west of the ruins.
Edit: Also, it would be really nice to have that list of shard locations you've been working on. Could you post it here?
Edit #2: Got him again; his name is Nodmor and this time he was roaming on the north side of the ruins.
Edited, Oct 18th 2009 7:49am by Gladestrider