Eureka with the blue

[SpiralMask]

Honestly a weird choice not to let BLUs enter Eureka. It's old content that could be revitalized by BLUs having fun in it or just people wanting to use BLUs for actual grinding(relics). When you've capped spells and instances, this could be the best place for BLUs to keep using the job instead of waiting till next update, whenever that will be.

in all likelihood the devs don't want BLUs "ruining" people's previous BA clears (which could be mitigated by just having it give BLU achievements when playing a BLU rather than the normal ones but whatever), which iirc was the cited reason why BLU doesn't get to even attempt ultimates content.

edit: could also be some balancing issues with elemental levels and BLU's weird spell scaling (not requiring a mainhand weapon, etc)