I'll start:
Level 8-15 can be soloed well in the past starter zones.
23-25: lycopodiums in rolanberry S and other areas adjacent to Jeuno seem to be an ideal EXP camp. They don't aggro or link, don't have dream flower, can be exp'd on with sigil bonuses and, best of all, there are sprites nearby (or at least 1...) It also gets high traffic during Campaign, so you probably wont have to worry about raises since either a campaign player or a sprite is probably going to come by you. Oh and I almost forgot, the fake aggro makes it possible to occasionally pull 2 at once with no ill effects
28-32 Rock Eater in Grauberg
Decent number of spawns. Spawns start pretty much from the zone line to N. Gust just need to watch for the roaming Goblin Skirmisher as you move farther in. No pixie to my knowledge.
36-41: Colibri and Ladybugs in E Ronfaure S. They're pretty easy and don't link, you only have to watch out for aggro from ladybugs during the day. The only TP move that ladybugs use at night is Sudden Lunge, a single target damage + stun + knockback. There are camps all over the place, but a good one is near the place that would be the zone to W Ronfaure in the future. Ladybugs also have a bit higher stats during the day.
35-40: Beetles in Meriphataud Mountains S D-6.
43-46: Lynxes on the northish end of Meriphataud Mountains S. Rather than having the THFish traits of normal Coeurls, they have WARish traits which means manageable evasion! They also have Charged Whisker, which does some AOE lightning damage, but it's not hard to deal with. About F5/G5 is a decent camp iirc
42-44: Crawers in Rolanberry S around Taru NPCs
65-66sh: Grauberg Hippogryphs in Grauberg from F-9 to G-7. 15% exp bonus! Attacks fast so they're kind of dangerous for NIN tanks, PLD is much better for them. However, if you have Elegy+Slow, NIN tank is probably preferable since you can avoid Fantod. Fantod gives a Boost effect that makes the next attack they land deal tons of damage (800ish). Kind of evasive. They have a few more semi-nasty tp moves, but they are not that hard to survive.