Headed to Akheva on my 100 Necro, to kill Shar for the rune while Wizzy camped another mob for one of the other runes for her 1.5 pre-quest.
Found Shar directly west of Shei, so northern most west corner on map. Shar died pretty quickly but brought friends. My pet didn't do much damage, but it only took one DoT and a Nuke for good measure to bring him down. If you're lower level, you'll want to bring a couple of friends.
I don't know what the respawn timer is, but killed at 10:00 am EDT on 5/13/15 on The Rathe.