Just finished my champ rewards so good luck to you. This season is rough because 2s gets the MMR correction more. There is like only 4~5 days left so if you grind you can still make the diamond rewards. (although this season's reward looks kinda meh, like many other seasons.)
I have the diamond rewards already, and I've never been champ. I just did snow day for the first time this season and got ranked D1-1 there, so I think I should probably be D2 or D3 in 2s if I get a reliable teammate.
I only play snow days for the challenge unlocks, my MMR is falling like all the way to gold3/plat1.
I think if you are consistent enough on defense getting up to champ is not an issue. Most people just do riskier decision. And onward to high champ or even GC I think it's the battle of field sense, touch reading, and punishing mistakes proper.(it's work pretty well for me and my rank is slowly climbing even with the season reset.)