Ozball
46
Was changed it seems. I some how missed this post (and the one you linked) in my searching earlier today but:
Gives a possible updated one
CHANCE = (LIMIT * MASTERY) / (MASTERY + DECAY)
New: LIMIT = 0.73 & DECAY = 62
Old: LIMIT = 1 & DECAY = 100
This seems reasonably accurate based on my current masteries.