What's your first impression of Eureka?

[Tinibou]

if we're grouped with him, we get zero experience from every single normal mob in the place. The level gap between him and us is so high that grouping with him shuts us down entirely.

It won't be fixed since it's how the leveling system in the whole game works. You can't team with someone that is 10 level above you else you get no xp from mobs. The same rule applies for Eureka.
But you should be able to create a kind of "synced team" with friends to be able to do contents like that. Too bad that you can't...