There are actually at least 3 single spawns that i know of. I added the /loc of two to the Wiki Page for the Sarnak Courier (thnx to mcoy for pointing me to the one between the big trees
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All in all, i have been camping the Ring now for over 15h last week on a 34 Enchanter, no luck yet.
Adds can be really annoying, especially if you get 2 higher level ones, such as Goblin Soothsayers, at once.
Personally i wouldnt try that camp below lvl 20, probably not even below 24.