It would be a nice addition to add this for people who has completed the dungeon once since the tediousness of clicking retreat or the like is getting too much and just an honest waste of time.

Imo, dungeons are meant to be lengthy, no matter if its the first/second/last time you run them.
This is kinda consistent in many games (especially rougelike and MMOs) where there's a dungeon and multiple rooms with regular monsters in between the beginning and the boss room. Without an inbetween, the dungeon wouldn't be much of a dungeon, but just an instant bossfight.

I don't retreat in dungeons myself, because I always thought that fighting is the only way to make progress.

You only need to move to the puzzles for it to progress no battles are needed and regarding MMO type styles they can do this since its in real time and not as tedious do to constant clicking.

I never retreated from every single battle to get to the puzzles, but then again, I thought battles were the only way to progress. If both battles and retreating were tedious, the whole dungeon would be tedious.

As for real time vs clicking, you might see that in the new zones with maps (in Astryl's Vale and festival zones), they have maps to navigate. The admins intend to revamp all the zones (old zones and dungeons included) to have maps, so Sylestia's exploration feature will be, in the future, closer to a rogue-like dungeon crawler thank just clicking.

So for now, it'd be constant clicking to get through places, but I still think any dungeon, whether real time or turn based (clicking does count as turns), deserve an inbetween between the beginning, the puzzles, and the bosses.

Oh! Oh yeah I forgot about that.

Because of the old regions are going to be revamped soon[ish?] I doubt any big changes are going to be made to the coding. While I do like your suggestion [I don't much do the dungeons but when I do, I utilize the retreat feature until an event is triggered. -lazy-] It probably won't be implemented because of this. It's like how Krin said that they weren't going to fix layering issues on the pets that were going to be redesigned.

Um, the dungeons are designed to give you better drops than normal hunting. To get to those drops, you have to go through the dungeon. As in, fight your way through. I don't see Krin implementing a shortcut like this any time soon. It doesn't take long to get through them anyway, compared to dungeons in other games, so I really don't see the problem. Personally I fight my way through them and rarely if ever run, it takes about the same amount of time, and you get the random drops of extra stuff as you go along. But to each their own.