Bluetracker
Tracks Blizzard employees across various accounts.
Minimum win rate needed in ranked play
Was curious to figure out what would be the minimum win rate needed to progress in ranked play given the win streak bonus star.
Someone can probably do this better than me given that I have no knowledge of statistics, but I set out to generate a set of 10k values following a binomial distribution. Using excel's analysis toolpak and the bernoulli distribution, we can specify the probability of either value being a 1 or a 0 (i.e. the win rate).
The next column has a very simple formula to decide whether the outcome of the match should be -1 star, +1 star, or +2 stars in the event that this follows two previous "wins".
Anyway, with this, I have narrowed down the win rate that would give us a net "star output" >1 over these 10k games to be between 45.3% and 45.4%.
tl,dr: a win rate of 45.4% is technically enough to progress in ranked play (albeit at a ridiculously slow rate)
Iksar
Its interesting, but not very useful to know the answer to this question. I would much rather know what win rate I would need to reach X ranking over Y games. Where X is my goal rank and Y is an approximation of the amount of games I'll actually be able to play.