If you are looking to just grind max xp/hr I found just east of Queensdale there is a small pond which 3 elementals and about 8 gobs spawn lvl 27/28ish. We were in a full party with 2 healers ranging from 23 to as much as 34 at times. There are two double fates that pop in the area, one to the north, one to the east and about 6-8 other random ones in the area. Keep map open and run to a fate soon as it pops killing pond mobs during downtime. XP assuming you are getting gold on fates is 120k ish an hour. More if your group is coordinated enough to incorporate Camp Tranquil Fates (involves teleporting) The 2 double fates were boss types and it seemed to cap out at 14.4k xp.