Do monks use weapon damage? I can't remember.
If weapon damage matters, you'll want a slower mainhand. Either brushwood blade (alliance) or sinister scimitar. For OH, you'll want the highest ilvl you can get (34 from invasions, 27 from BG crate).
If weapon damage doesn't matter, you'll want 2x of the highest ilvl. You can use ilvl 24 things until you get the better ilvl stuff, so shadowfang is tied with every other ilvl 24 item (including heirlooms). So its mostly swag at this point.