So from events you occasionally win a single booster here n there.
What I’ve noticed is there no text saying “chance of rare” anymore and I have not pulled one from a single “won” booster since the update.
Are we to presume that single boosters do not contain rares??
I just pulled a puppetmaster from a Kaladesh booster I won. So there is a chance. I guess the usual 1%? 
Usual chance is about 20%
I just got 3 rares from my NoP progression reward booster.
That seems high. That would average a rare in every pack. What do you think this is? Paper magic? 
Ok so in like 10 ish progression boosters nothing.
Just opened one from Nodes of Power and…
Aethersworn Roc - Mythic
Wildest Dreams - Rare.
It’s like buses with these boosters…