If you do better than your own average in terms of ACS, you get a performance bonus. As you would imagine, this does favor duelists most of the time. Now that you are playing support it will be hard to beat your own average and you will need to rely on just winning consistently rather than the performance bonus until you fix your average ACS.

And in my experience, it's pretty punshing. Usually it more than one win to make up for a loss. To progress faster, you just need to win but also do well personally in the match, whether win or loss as the performance bonus is a big deal. I got out of iron with a less than 50% winrate thanks to the performance bonus.

If you're good enough to convince the algorithm that you are a smurf then you will be rewarded might get double rank ups, but in that case you need to consistently pop off and consistently win like a Radiant playing in iron theoretically would.