Although it's still early days, it's looking to me like the deep dungeon concept is very successful with lots of people participating and spending a lot of hours on it. There are a couple rough edges and while negative feedback is helpful, I think it's also important to reflect on what is does right and analyse why it is successful.
(1) Low barrier of entry. Just the fact that you can enter from Lv17 and your usual gear level is irrelevant makes it so inclusive. Both new players and lapsed players who haven't been keeping up with gearing can jump right in to relevant content without hindering anyone.
(2) Flexible floor rewards. The way it gives either EXP or tomestones depending on your need is a big deal. This way people with different goals have something they can play together. Any battle content needs tomestones to be truly successful, otherwise players who don't have much time to play will need to revert back to the linear dungeons/ roulettes to meet their weekly caps.
(3) Weapons. The game needed more options for relevant weapons and deep dungeon delivers. For whatever reason, crafted weapons are kept far behind, with the IL 180 Bismarck ones being the strongest currently available. That left the only options for IL 230+ weapons being Savage raids, Anima or 7 weeks lockout of normal raid. The new Padjali weapons are a nice addition which is a preferable grind for many people.
(4) Yay for randomness. Until now, PVE content has typically been very linear, exactly the same patterns every time you play. Dungeons in particular could get tiresome fast, with the same enemies in the same positions on repeat forever. Deep dungeon is a brilliant change, always being unfamiliar with its layouts and enemies and threat of hidden traps. If you have to grind something, a bit of randomness goes a long way.
(5) Flexible composition. This is just great for queue times, letting people group up on any jobs or classes, even if healers or tanks are not available. We are rarely afforded this kind of freedom and it's another element which keeps things fresh and interesting as our approach changes depending on what kind of composition the matchmaking gives us.
(6) Honorable mentions... long-term unique rewards from gelmorran potsherds are nice... consumables like potions, echo drops and phoenix down becoming useful again... succubus/manticore transformations are fun to use...
Good job, keep it up! I'm looking forward to future deep dungeons and the remaining floors of Palace of the Dead.