I think most of them we've lightly discussed, things like spawn mechanics, difficulty level, and drops. Depending on how it's set up, mob drops could be tweaked, or add an extra room with chests and allow mobs to have a chance to drop keys, similar to how normal dungeons have chest rooms and you get keys from mobs in the orb rooms.
The duration of how long the dungeon entrance stays open, and how easily identifiable the difficulty of the dungeon is before
entering is somewhat important to. Say i got 2-3 people i want to play with and we all want to do the dungeon. Well obviously it's not a 100% chance that we're gonna have the dungeon show up every exploration attempt. And following around someone for 10 minutes while they try to find it doesn't sound fun, conversely splitting up could make it difficult for friends to join you in time as we only have one channel so it's not like we can search the same spot across multiple channels.
A short duration for the entrance is all well and fine, but i would at least like enough time to be able to be like "I found an exploration dungeon, anyone want to give me a hand?" and have enough time to get a response as well as use a summon cap, yes i'm actually suggesting a summon cap as a reason to keep the dungeon appearance reduced, and let the person join me while feeling i can leisurely enter without going "Well, you took too long so i'll have to find a new dungeon." and people leaving because screw the wait.
This is also why identifying the difficulty ahead of time is important, so i don't invite a lv 100 into a lv 500 dungeon. Cuz if i legit want something out of the dungeon and need a hand, that's going to massively backfire. And with some rng application on that dungeon, that could turn into a tedious task. The more RNG involved, the worse it can get.
I suppose if you want to just make it a solo dungeon, you could circumvent most of that, but at the same time people would get bored repeatedly solo grinding the same thing, when they also have to spend their time searching for it before hand, and the rng issue will still apply, just no frustration of dealing with others.
Again, mobs inside are a big deal to me as well. No one wants to waste, say 10 minutes of their time in a dungeon, only to suddenly get thrown a mob with immunities to the skills you use. I can smash real good now, but that means nothing in the face of a wight. Similarly, i don't care how good of a mage you are, when a ghost shows up. All you're gonna be doing is trying to keep it from casting, and basically nothing else. This is a great late/end game tool, and i'm not opposed to it, but if something like it is used, then we would need a way to know to expect these mobs. For example, have the dungeons in zardine region have a chance at peaca mobs, or maybe include a peaca mob as a boss. Meanwhile, Rano could be rundal mobs or something. It's not a clear cut announcement on what you'd see each run, possibly, but you would have a rough idea of what to expect. You'd think 'okay, i'm not strong enough to handle peaca mobs yet, so i'll steer clear of zardine dungeons.' While others will be thinking "I'm able to do rundal, but those blasted ship rats are a problem. Better find a meat shield."
I'm sure there's various ways to approach the multitude of problems that bother me, but things seem a little foggy on the topic atm. So clearing up what would be acceptable and wouldn't, what is actually desired versus what you'd compromise, as well as how others feel, would be a boon to the topic. And it'd save a lot of exposition.