When I first went into Eureka i didn't like it very much. I thought it was similar to Diadem but with fates that occasionally spawn.
Then a couple days later players found out that you had to force the NMs to spawn, similar to FF11's lottery spawn system. Where killing an enemy had a low chance that a NM would respawn in it's place. I started to like it a little more then.
The things I really liked about Eureka, were that it encouraged players to group up to tackle the NMs. I also liked that the whole instance encourages players to share information with each other to succeed inside. The quests, the NM spawn timers, killing wraiths to spawn pazuzu all needed players to work together to share information. It really felt more like an online RPG than duty findering the dungeons.
Things I didn't like were that it definately felt that it had that FF14 super-casual twist to it. The NMs could be attacked by the entire zone which leads to pretty much every NM monster just getting zerged down easily. You lose xp upon dying but only if you don't get raised. This leads to players just throwing bodies at the NMs until they die. I think there should be a smaller xp penalty for dying and getting raised. This would lead to players only taking on NMs that are around their level. And level 1-20 could be done in just a few days of semi-serious play.
Things i would improve are making the NMs only able to be fought by 1 party or maybe 1 alliance at a time to encourage players to split up and tackle different NMs instead of "the train". A small xp penalty for dying and getting raised to avoid players just throwing bodies at the NMs. Also more interesting ways to spawn the NMs.
Overall the content was a fun nostalgic trip to FFXI NM hunting and it was fun seeing some of the 11 bosses in there like Serket, Valkurm Emporer, and Simurgh. I liked the nod to FF11, but would like to see Eureka improved some more.