You're suggesting badges for winner of RND basically, since not everyone who qualified for an Act got a prize for it. As such, voting against your idea -.
I would be neutral if it was amended to people who met qualifications or something not dependent on coin tossing. e.g. 'D3-Act4' would be for the 10+ who qualified for act 4 and not only those who won.
Don't particularly care either way about such a badge, but I dislike the idea of having one you can't possibly earn except thru luck.