Ill start by saying that not everyone shares Micah's opinion. Im positive you will find a couple bits frustrating based on your posting history, but how you will react to the rest im not in a position to guess. However, what they refer to is still aways off yet and not in your immediate future.
As for your current exploration of the dark, it does last a little bit longer then the solo duty in front of you, but it shouldnt be too bad. Ill spoiler block this incase you/anyone who finds this in the future doesnt want precise details, but i am answering in case you do need a hard answer on how long the depressive episode could last. Specific spoiler answer below, read at your own discretion.
So if im placing your progress correctly, youre at the solo duty in the quest "Where Everything Begins". This fight shouldnt honestly be too hard. You play as yourself, and you have the NPCs helping you out. Youll spend 1 more quest in this area gathering information, that quest ends with sending you to a new slightly more open area you havent seen yet. One quest exploring this new area. The final quest in the void sends you into a trial. When the trial is over you leave the thirteenth, and things will keep you busy on the source for awhile. So in total you have: solo duty, 3 quests that will stretch into a new space, and a trial. After that, its back to the sunshine.
With that said, if taking a break to work on the alt will make you happy then be happy. No one should want to take that from you.
Edit: And i see you updated while i was typing that. I dont remember that particular fight ever being a problem for people, but congrats on not getting stuck regardless. Continue on as you see fit.