Dragon soul optimization

Dragon soul is a new addition to the game. Besides giving some stat bonuses, it is supposedly something which is a prerequisite for other things when you max it out. So it would be important to know how much time you need to max it out. I would like to give you some help with that.

Dwmedia wrote a few things on the Wartune forum, for which I am very thankful. So let's suppose the following, based on what we have now:

Dragon soul have 20 levels in total, which needs an approx. total of 900 dragon essences.
In Nirvana NM, we can get 4 essences per run. In lych, you get essences for minis as well, but only 1 per boss, so I assume Nirvana is still better source (if you can do it).
The second resource costs balens: you have to run the necropolis. You get dragon essences depending how far you get:
lvl 5 = 1 x Essence 
lvl 10 = 2 x Essences
lvl 15 = 3 x Essences
lvl 20 = 4 x Essences
lvl 25 = 5 x Essences
lvl 30 = 6 x Essences
I'm at lvl 20, so I get a total of 10 Essences per run.

Ok, there are the following options:

1.) Collect essences only from MPD. In this case, I need 900 / 4 = 225 days to max out dragon soul.

2.) I get an average of 1 free crypt key from using skeleton keys and rolling the guild wheel per day. If I use these to do a necropolis every 3 day instead of using it in catacombs, I need 900 / 7.3 = 123 days.

3.) If I buy 2 crypt keys and do necropolis every day, I need 900 / 14 = 64 days (9900 balens, ouch).

The question is, when do I need my dragon soul maxed out? As we have seen, Proficient City is much slower at adding content than 7Roads. So it can be anything between 2 and 5 months. My guess would be 3 months (but really, no one can tell).

Conclusion. If you are pretty ahead in necropolis (level 20 or further), and dont want to spend 10k balens on some blind shot, you should stop using crypt keys in cata and start using them in necropolis. If you are not so ahead in necropolis, try to get a bit further (warrior's call helps a lot!). I wouldn't recommend buying a large amount of crypt keys now. We don't know much yet, maybe the numbers are different, maybe we have more time, maybe there will be a crypt key sale, and definitely there will be a big spender event soon. Just wait, and do necropolis for free when you can. Patience always saves a lot of balens.