Back in the days in ARR, what I use to do was after I did all that I could with feeding and challenge log XP, was farm Water Sprites in Urth’s Fount in the South Shroud. They were level 50 and gave out the Maximum XP in the open world. After a while , it was getting popular with Chocobo XP hunters, so I moved on to the Northern Thanalan and farmed the Level 50 Magitek Robots (I cant remember their exact name). That was better for me as I use to sell their drops which sold for a decent amount back then. I had already a predetermined path to walk around and kill all the Magiteks and by the time I made my round, the 1st one spawned back. I just kept at it like this until my Chocobo hit level 20. It took some time, but I found it efficient. As far as today, maybe you can farm whatever mob you want in the Tempest. I don’t know if there are any level 80 mobs, but any Level 79 would do. Fates are Ok, but you lose time flying around from Fate to Fate. I just stick to a group of mobs and cycle through them as they respawn. I don’t recall Fates giving Chocobo XP for completing the Fate like you get, but I wish they did as that would’ve helped more. They only get XP per each kill and that’s based on the level of the mob which is usually lower level than the non Fate mobs in the area, so I would just stick with regular non Fate mobs if Chocobo XP is what you’re after.