A note about the Rathe Necros: Findlegrob is in an Undead Tower near the Lake Rathe zone, surrounded by sundry lower-level undead (skeletons, zombies, some lower drybones). At 30th we were able to pull him from the tower without getting any of the surrounding undead, and we had a great time killing him again and again. He dropped the Rune almost every time, I'd say 3 of 5 kills.
There is another Undead Tower close to the Feerott zone, and this is the home of Bindlegrob and Sindlegrob. Do not be fooled! They are both in there! Sindlegrob is inside, just to the right of the door. You cannot see him unless you actually enter the tower or pull his buddy Bindlegrob. These Necros were blue to us, and things could get nasty (a 30 Magician and 31 Shaman), but the only time deaths resulted was when the Endure Magic wore off during a fight (doh!) and again when the Mage pet went tearing off after a zombie instead of helping with the Necros (DOH!). If we'd had a tank with us, this would have been easier. These guys drop pretty quickly with Malise followed by two nuking.
At both towers, the surrounding undead can respawn as a Giant Skeleton, who is a pain to have join in this fight, so if you don't have to kill the clutter, leave it alone.