FATE result (level 18 near Aleport, where FATEs are levels 10-18):

Time: 23 minutes
EXP: 49749
EXP/min: 2163

So at level 18, FATEs in Aleport are 2.27 to 2.53 times the experience rate of dungeons. That may be partly a question of the efficiency of the area, with fewer players, fewer FATEs, a larger area to cover, and being overleveled for most of the FATEs in the area. I can try again at level 20, with a fresh dungeon and fresh FATE area to compare, but I don't think it's going to get any more favorable for dungeons.