I think Alla needs to change common to rarity because I hunt in NC all the time and dont see Kyv Bowstrings drop and they should be made common, where as the no drops should be made rare
I got mine solo by hunting Kyvs in NC. Pull them from throughout the zone to the valleys at the WoS or DS zone and kite them down. The trick is that you can pull, invis, head into the valleys, and you get no adds - the murks and other mobs in the valleys just ignore the kyvs as they go by. I'm a bard, but you can do this as any class that can run fast and invis (I wasn't using any bard pull tricks).
I pulled the 3 NE of the DS zone (1 is the PH for Pixt Trent) to the DS zone line, the 2 by the bridge close to the WoS zone line to the WoS zone, and a few that are in the middle to either camp. I chant kited them down and was able to clear 7 or 8 before repops started (20 min respawn time).
I killed 46 to get my 2 kyv bowstrings. It took me about 6 hours. I also got 2 runes, 3 OK caster cloaks, 1 slugworms, 4 chain OOW armor quest pieces, and 1 Drakescale Shield, so it turned out to be a pretty good loot camp. The XP was pretty sad though.
Drops in NC off of Kyv Heartstrikers. I spent about 8 hours trying to get a muramite dispatch and saw two of these drop in that time, so they are fairly rare.