We still don't have enough data gathered, but according to a Reddit user, the Mystic Bookmarks in the secret shop appear on a 2% chance, while the Covenant Bookmarks appear on a 4% chance.
If those numbers are not flawed, you can expect out of 1000 Skystones and 4 million gold spent in refreshes:
65 Covenant Bookmarks (13 pulls), 350 Mystic Bookmarks (7 pulls).
So if you don't mind slowing your gearing progress (Gold = progress), you can potentially convert those Skystones in Mystic Pity + a lot of bookmarks for regular banners.
Assuming the Mystic Bookmarks data is correct:
1. You can expect as f2p about 1000 skystones (if not more) weekly from login, PVP rewards, etc...
2. You can expect as f2p in a competent guild about 150 mystics per week from Guild War.
3. You can expect as f2p about 50 more mystics from Hunts rewards.
If 1000 skystones = 350 mystics
You can expect a total of 550 Mystics per week (11 pulls)
To reach 10.000 Mystics this way, so with 0 purchases, you need 18 weeks. (4 months and half).
Considering you can target the unit you want rather than have it randomly given to you, this is not terribly bad. It's at least definitely better than what we had before.
My refund experience was bad as expected. I had about 150 Galaxy Bookmarks being refunded.
I found 27 times 3* heroes and 3 times 4* heroes (all dupes and I still miss many).
I'm not even upset because I honestly didn't expect anything from it. I knew somebody would be super lucky and most of us would be unlucky.
I was ready to whale for ML Ravi (between the Mystic refunds and my gacha budget I had potentially enough to hit the pity).
I was "lucky" though and pulled her within 3500 mystics.
Overall, I think releasing this huge amount of Galaxy Bookmarks will cause a lot of emotions, especially from people that didn't find anything and see everybody else getting multiple heroes they wanted.
It was/it's a dangerous move on their part.
In retrospect, giving the whole community a guaranteed reward would have been better imho.
The new Mystic system though, now that we kind of know the Mystics in the Secret Shop are not as rare as I thought, can let f2p players and low spender plan ahead very well.
The new ML heroes being every 8 weeks instead of 4 also helps accumulating resources.
Mystics is definitely the way to go to get those special units and Galaxy is a bonus you shouldn't rely on.
Let's see what will be the whole community reaction, especially Korea, and let's see what happens next.
Overall, my most welcomed change is and still is the Pity on all the Covenant Banners. That alone makes me enjoy the game 1000 times more.
PS: ML Ravi is interesting but she's doesn't feel a meta changing unit to me. I still feel Fire Ken is the superior HP based bruiser. I hope to be proven wrong.