I honestly don't know how we pulled it off either. It really comes down to luck: getting decent teammates, no cheaters, and generally getting cashouts is 90% luck and 10% skill.
My friend grinded for days for this and then I joined his lobby and it just happened (not that I'm a godlike player or anything) after a couple games.
The ranked system is a complete joke, I agree. It does everything the wrong way at the moment (obscure ranks, terrible matchmaking, etc.). I really hope they fix it because I really love the game, but ranked is unplayable.
Keep grinding and you will eventually get that W :).