Why do you want to level that fast anyways? Does it really matter? At the end, FATE gives you Anemos Crystals wich are needed for the relic (the AF upgrade is part of the relic as well) and you can just level farming Anemos Crystals.

Once I hitted lv19 I already had enough Anemos Crystals to finish the relic weapon and the 5 upgrades of the Artifact.

Chaining mobs can give you good exp, but at the end of the day all you need is Crystals, so the optimal thing is to pop NM's around your level so you can farm the crystals, instead of wasting time on a too-high level FATE that will only give you a partial of it's exp and no crystals.


Maybe Chains should give Anemos Crystals and that would be a cool improvement, but I'm afraid you've been playing Eureka in the wrong way or in a way that you wasted a lot of time.