Something along the lines of WoW's Timeless Isle/Argus model, not a carbon copy but something similar. A large open world land that had something for everyone, a large range of rewards and different ways to play and enjoy it. Easy mobs, elite mobs, rare mobs, Fates, dailies, rep, minions, mounts, treasures, gathering, crafting, invasions, proper story chain, that sort of thing.
Eureka is basically the Fate train. That's it. That's all you do there.
How could they develop for 17 months, create a huge detailed island and only manage to come up with a single activity for it?