FnFn There are biosphere runs sometimes, and I'm sure guilds run constellation tower. There is plenty of difficult content out there, but the server is very accessible to solo players, and gravity made it possible to solo most content now.
I personally haven't done depths myself, and died at the boss in constellation tower (with a friend) so, I'm curious about those areas. Unfortunately, we can't make any of the current content harder, or it wouldn't be fair to anyone new. There was discussion regarding instances being more difficult, with rewards actually worth party play incentives. Not sure where we've gone from there, but I hope they implement something like that, or some custom fields which require large amounts of people, with an added quest which can possibly last a week. I wouldn't mind something like that.