I'm not sure about a "public dungeon". I thought Eureka itself was that, to be honest.
But a massive raid of 48 people has clearly been demonstrated to work, even though we've had to rely on Discord for grouping and smash our heads against these stupid portals. If the party finding and instance reserving was properly implemented I think a lot of people would like a little more difficulty than the mindless 24mans. But they need to realize that people are going to want to raid with their friends/team mates.
