Some info was released with a E3 interview. MrHappy made a video about it the other day.
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It will be another grind no matter what.
Relic has been a tool to help new players, like doing low-level dungeons so new players gets fast queues, or free runs on primals, or full parties on FATEs so new players can experience a world full of players everywhere etc... it has been always this strategy.
So expect another grind like the Yo-Kai event, wich happened at the same time when SE released the free to play version, so the potentially new players could see all the low-level maps full of people.
Gear is always just for glamour in the end. Always. Otherwise progression will stop.
I hope this Eureka weapon grind will not be tied to RNG too heavily. While light/Umbrites and such are usually a long grind, at least you know how close you are to finishing unlike with Yokai/Atma fate farming.
Supposedly they're supposed to only used Eureka for the relic.
It's going to be a grind for sure. After the 50 relic players specifically asked for the 60 one to be much less grindy and easier to obtain.
SE took that feedback and threw it in to a furnace.